├── LICENSE ├── README.md ├── diagrams ├── interview-template.png └── system-design-github-logo.png └── implementations ├── java ├── consistent_hashing │ └── ConsistentHashing.java ├── load_balancing_algorithms │ ├── IPHash.java │ ├── LeastConnections.java │ ├── LeastResponseTime.java │ ├── RoundRobin.java │ └── WeightedRoundRobin.java └── rate_limiting │ ├── FixedWindowCounter.java │ ├── LeakyBucket.java │ ├── SlidingWindowCounter.java │ ├── SlidingWindowLog.java │ └── TokenBucket.java └── python ├── consistent_hashing └── consistent-hashing.py ├── load_balancing_algorithms ├── ip_hash.py ├── least_connections.py ├── least_response_time.py ├── round_robin.py.py └── weighted_round_robin.py └── rate_limiting ├── fixed_window_counter.py ├── leaky_bucket.py ├── sliding_window_counter.py ├── sliding_window_log.py └── token_bucket.py /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 3, 29 June 2007 3 | 4 | Copyright (C) 2007 Free Software Foundation, Inc. 5 | Everyone is permitted to copy and distribute verbatim copies 6 | of this license document, but changing it is not allowed. 7 | 8 | Preamble 9 | 10 | The GNU General Public License is a free, copyleft license for 11 | software and other kinds of works. 12 | 13 | The licenses for most software and other practical works are designed 14 | to take away your freedom to share and change the works. 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It is safest 630 | to attach them to the start of each source file to most effectively 631 | state the exclusion of warranty; and each file should have at least 632 | the "copyright" line and a pointer to where the full notice is found. 633 | 634 | 635 | Copyright (C) 636 | 637 | This program is free software: you can redistribute it and/or modify 638 | it under the terms of the GNU General Public License as published by 639 | the Free Software Foundation, either version 3 of the License, or 640 | (at your option) any later version. 641 | 642 | This program is distributed in the hope that it will be useful, 643 | but WITHOUT ANY WARRANTY; without even the implied warranty of 644 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 645 | GNU General Public License for more details. 646 | 647 | You should have received a copy of the GNU General Public License 648 | along with this program. If not, see . 649 | 650 | Also add information on how to contact you by electronic and paper mail. 651 | 652 | If the program does terminal interaction, make it output a short 653 | notice like this when it starts in an interactive mode: 654 | 655 | Copyright (C) 656 | This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. 657 | This is free software, and you are welcome to redistribute it 658 | under certain conditions; type `show c' for details. 659 | 660 | The hypothetical commands `show w' and `show c' should show the appropriate 661 | parts of the General Public License. Of course, your program's commands 662 | might be different; for a GUI interface, you would use an "about box". 663 | 664 | You should also get your employer (if you work as a programmer) or school, 665 | if any, to sign a "copyright disclaimer" for the program, if necessary. 666 | For more information on this, and how to apply and follow the GNU GPL, see 667 | . 668 | 669 | The GNU General Public License does not permit incorporating your program 670 | into proprietary programs. If your program is a subroutine library, you 671 | may consider it more useful to permit linking proprietary applications with 672 | the library. If this is what you want to do, use the GNU Lesser General 673 | Public License instead of this License. But first, please read 674 | . 675 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 |

2 | 3 |

4 | 5 | This repository contains free resources to learn System Design concepts and prepare for interviews. 6 | 7 | 👉 Subscribe to my [AlgoMaster Newsletter](https://bit.ly/amghsd) and get a **FREE System Design Interview Handbook** in your inbox. 8 | 9 | ✅ If you are new to System Design, start here: [System Design was HARD until I Learned these 30 Concepts](https://blog.algomaster.io/p/30-system-design-concepts) 10 | 11 | ## 📌 System Design Key Concepts 12 | - [Scalability](https://blog.algomaster.io/p/scalability) 13 | - [Availability](https://blog.algomaster.io/p/system-design-what-is-availability) 14 | - [CAP Theorem](https://blog.algomaster.io/p/cap-theorem-explained) 15 | - [ACID Transactions](https://blog.algomaster.io/p/what-are-acid-transactions-in-databases) 16 | - [Consistent Hashing](https://blog.algomaster.io/p/consistent-hashing-explained) 17 | - [Rate Limiting](https://blog.algomaster.io/p/rate-limiting-algorithms-explained-with-code) 18 | - [SPOF](https://blog.algomaster.io/p/system-design-how-to-avoid-single-point-of-failures) 19 | - [Fault Tolerance](https://www.cockroachlabs.com/blog/what-is-fault-tolerance/) 20 | - [Consensus Algorithms](https://medium.com/@sourabhatta1819/consensus-in-distributed-system-ac79f8ba2b8c) 21 | - [Gossip Protocol](http://highscalability.com/blog/2023/7/16/gossip-protocol-explained.html) 22 | - [Service Discovery](https://blog.algomaster.io/p/service-discovery-in-distributed-systems) 23 | - [API Design](https://abdulrwahab.medium.com/api-architecture-best-practices-for-designing-rest-apis-bf907025f5f) 24 | - [Disaster Recovery](https://cloud.google.com/learn/what-is-disaster-recovery) 25 | - [Distributed Tracing](https://www.dynatrace.com/news/blog/what-is-distributed-tracing/) 26 | 27 | ## 🛠️ System Design Building Blocks 28 | - [APIs](https://blog.algomaster.io/p/whats-an-api) 29 | - [Content Delivery Network (CDN)](https://blog.algomaster.io/p/content-delivery-networks) 30 | - [Proxy vs Reverse Proxy](https://blog.algomaster.io/p/proxy-vs-reverse-proxy-explained) 31 | - [Domain Name System (DNS)](https://www.cloudflare.com/learning/dns/what-is-dns/) 32 | - [Caching](https://blog.algomaster.io/p/4d7d6f8a-6803-4c7b-85ca-864c87c2cbf2) 33 | - [Caching Strategies](https://blog.algomaster.io/p/top-5-caching-strategies-explained) 34 | - [Distributed Caching](https://blog.algomaster.io/p/distributed-caching) 35 | - [API Gateway](https://blog.algomaster.io/p/what-is-an-api-gateway) 36 | - [Load Balancing](https://blog.algomaster.io/p/load-balancing-algorithms-explained-with-code) 37 | - [Databases Types](https://blog.algomaster.io/p/15-types-of-databases) 38 | - [SQL vs NoSQL](https://blog.algomaster.io/p/sql-vs-nosql-7-key-differences) 39 | - [Database Indexes](https://blog.algomaster.io/p/a-detailed-guide-on-database-indexes) 40 | - [Consistency Patterns](https://systemdesign.one/consistency-patterns/) 41 | - [HeartBeats](https://blog.algomaster.io/p/heartbeats-in-distributed-systems) 42 | - [Circuit Breaker](https://medium.com/geekculture/design-patterns-for-microservices-circuit-breaker-pattern-276249ffab33) 43 | - [Idempotency](https://blog.algomaster.io/p/idempotency-in-distributed-systems) 44 | - [Database Scaling](https://blog.algomaster.io/p/system-design-how-to-scale-a-database) 45 | - [Data Replication](https://redis.com/blog/what-is-data-replication/) 46 | - [Data Redundancy](https://blog.algomaster.io/p/489440f1-9c80-4241-9ec8-de156964c3b9) 47 | - [Database Sharding](https://blog.algomaster.io/p/what-is-database-sharding) 48 | - [Database Architectures](https://www.mongodb.com/developer/products/mongodb/active-active-application-architectures/) 49 | - [Failover](https://www.druva.com/glossary/what-is-a-failover-definition-and-related-faqs) 50 | - [Bloom Filters](https://blog.algomaster.io/p/bloom-filters) 51 | - [Message Queues](https://blog.algomaster.io/p/message-queues) 52 | - [WebSockets](https://blog.algomaster.io/p/websockets) 53 | - [Checksums](https://blog.algomaster.io/p/what-are-checksums) 54 | - [Microservices Guidelines](https://newsletter.systemdesign.one/p/netflix-microservices) 55 | - [Distributed Locking](https://martin.kleppmann.com/2016/02/08/how-to-do-distributed-locking.html) 56 | 57 | ## ⚖️ System Design Tradeoffs 58 | - [Top 15 Tradeoffs](https://blog.algomaster.io/p/system-design-top-15-trade-offs) 59 | - [Vertical vs Horizontal Scaling](https://blog.algomaster.io/p/system-design-vertical-vs-horizontal-scaling) 60 | - [Concurrency vs Parallelism](https://blog.algomaster.io/p/concurrency-vs-parallelism) 61 | - [Long Polling vs WebSockets](https://blog.algomaster.io/p/long-polling-vs-websockets) 62 | - [Batch vs Stream Processing](https://blog.algomaster.io/p/batch-processing-vs-stream-processing) 63 | - [Stateful vs Stateless Design](https://blog.algomaster.io/p/741dff8e-10ea-413e-8dd2-be57434917d2) 64 | - [Strong vs Eventual Consistency](https://blog.algomaster.io/p/7d9da525-fe25-4e16-94e8-8056e7c57934) 65 | - [Read-Through vs Write-Through Cache](https://blog.algomaster.io/p/59cae60d-9717-4e20-a59e-759e370db4e5) 66 | - [Push vs Pull Architecture](https://blog.algomaster.io/p/af5fe2fe-9a4f-4708-af43-184945a243af) 67 | - [REST vs RPC](https://blog.algomaster.io/p/106604fb-b746-41de-88fb-60e932b2ff68) 68 | - [Synchronous vs. asynchronous communications](https://blog.algomaster.io/p/aec1cebf-6060-45a7-8e00-47364ca70761) 69 | - [Latency vs Throughput](https://aws.amazon.com/compare/the-difference-between-throughput-and-latency/) 70 | 71 | ## 🖇️ System Design Architectural Patterns 72 | - [Client-Server Architecture](https://blog.algomaster.io/p/4585cf8e-30a4-4295-936f-308a25cb716c) 73 | - [Microservices Architecture](https://medium.com/hashmapinc/the-what-why-and-how-of-a-microservices-architecture-4179579423a9) 74 | - [Serverless Architecture](https://blog.algomaster.io/p/2edeb23b-cfa5-4b24-845e-3f6f7a39d162) 75 | - [Event-Driven Architecture](https://www.confluent.io/learn/event-driven-architecture/) 76 | - [Peer-to-Peer (P2P) Architecture](https://www.spiceworks.com/tech/networking/articles/what-is-peer-to-peer/) 77 | 78 | ## ✅ [How to Answer a System Design Interview Problem](https://blog.algomaster.io/p/how-to-answer-a-system-design-interview-problem) 79 | 80 | ## 💻 System Design Interview Problems 81 | ### Easy 82 | - [Design URL Shortener like TinyURL](https://blog.algomaster.io/p/design-a-url-shortener) 83 | - [Design Leaderboard](https://systemdesign.one/leaderboard-system-design/) 84 | - [Design Content Delivery Network (CDN)](https://www.youtube.com/watch?v=8zX0rue2Hic) 85 | - [Design Parking Garage](https://www.youtube.com/watch?v=NtMvNh0WFVM) 86 | - [Design Vending Machine](https://www.youtube.com/watch?v=D0kDMUgo27c) 87 | - [Design Distributed Key-Value Store](https://www.youtube.com/watch?v=rnZmdmlR-2M) 88 | - [Design Distributed Cache](https://www.youtube.com/watch?v=iuqZvajTOyA) 89 | - [Design Authentication System](https://www.youtube.com/watch?v=uj_4vxm9u90) 90 | - [Design Unified Payments Interface (UPI)](https://www.youtube.com/watch?v=QpLy0_c_RXk) 91 | ### Medium 92 | - [Design WhatsApp](https://blog.algomaster.io/p/design-a-chat-application-like-whatsapp) 93 | - [Design Spotify](https://blog.algomaster.io/p/design-spotify-system-design-interview) 94 | - [Design Distributed Job Scheduler](https://blog.algomaster.io/p/design-a-distributed-job-scheduler) 95 | - [Design a Scalable Notification Service](https://blog.algomaster.io/p/design-a-scalable-notification-service) 96 | - [Design Instagram](https://www.youtube.com/watch?v=VJpfO6KdyWE) 97 | - [Design Tinder](https://www.youtube.com/watch?v=tndzLznxq40) 98 | - [Design Facebook](https://www.youtube.com/watch?v=9-hjBGxuiEs) 99 | - [Design Twitter](https://www.youtube.com/watch?v=wYk0xPP_P_8) 100 | - [Design Reddit](https://www.youtube.com/watch?v=KYExYE_9nIY) 101 | - [Design Netflix](https://www.youtube.com/watch?v=psQzyFfsUGU) 102 | - [Design Youtube](https://www.youtube.com/watch?v=jPKTo1iGQiE) 103 | - [Design Google Search](https://www.youtube.com/watch?v=CeGtqouT8eA) 104 | - [Design E-commerce Store like Amazon](https://www.youtube.com/watch?v=EpASu_1dUdE) 105 | - [Design TikTok](https://www.youtube.com/watch?v=Z-0g_aJL5Fw) 106 | - [Design Shopify](https://www.youtube.com/watch?v=lEL4F_0J3l8) 107 | - [Design Airbnb](https://www.youtube.com/watch?v=YyOXt2MEkv4) 108 | - [Design Autocomplete for Search Engines](https://www.youtube.com/watch?v=us0qySiUsGU) 109 | - [Design Rate Limiter](https://www.youtube.com/watch?v=mhUQe4BKZXs) 110 | - [Design Distributed Message Queue like Kafka](https://www.youtube.com/watch?v=iJLL-KPqBpM) 111 | - [Design Flight Booking System](https://www.youtube.com/watch?v=qsGcfVGvFSs) 112 | - [Design Online Code Editor](https://www.youtube.com/watch?v=07jkn4jUtso) 113 | - [Design Stock Exchange System](https://www.youtube.com/watch?v=dUMWMZmMsVE) 114 | - [Design an Analytics Platform (Metrics & Logging)](https://www.youtube.com/watch?v=kIcq1_pBQSY) 115 | - [Design Payment System](https://www.youtube.com/watch?v=olfaBgJrUBI) 116 | - [Design a Digital Wallet](https://www.youtube.com/watch?v=4ijjIUeq6hE) 117 | ### Hard 118 | - [Design Location Based Service like Yelp](https://www.youtube.com/watch?v=M4lR_Va97cQ) 119 | - [Design Uber](https://www.youtube.com/watch?v=umWABit-wbk) 120 | - [Design Food Delivery App like Doordash](https://www.youtube.com/watch?v=iRhSAR3ldTw) 121 | - [Design Google Docs](https://www.youtube.com/watch?v=2auwirNBvGg) 122 | - [Design Google Maps](https://www.youtube.com/watch?v=jk3yvVfNvds) 123 | - [Design Zoom](https://www.youtube.com/watch?v=G32ThJakeHk) 124 | - [Design Distributed Counter](https://systemdesign.one/distributed-counter-system-design/) 125 | - [Design File Sharing System like Dropbox](https://www.youtube.com/watch?v=U0xTu6E2CT8) 126 | - [Design Ticket Booking System like BookMyShow](https://www.youtube.com/watch?v=lBAwJgoO3Ek) 127 | - [Design Distributed Web Crawler](https://www.youtube.com/watch?v=BKZxZwUgL3Y) 128 | - [Design Code Deployment System](https://www.youtube.com/watch?v=q0KGYwNbf-0) 129 | - [Design Distributed Cloud Storage like S3](https://www.youtube.com/watch?v=UmWtcgC96X8) 130 | - [Design Distributed Locking Service](https://www.youtube.com/watch?v=v7x75aN9liM) 131 | - [Design Slack](https://systemdesign.one/slack-architecture/) 132 | - [Design Live Comments](https://systemdesign.one/live-comment-system-design/) 133 | 134 | ## 📚 Books 135 | - [Designing Data-Intensive Applications](https://www.amazon.in/dp/9352135245) 136 | 137 | ## 📩 Newsletters 138 | - [AlgoMaster Newsletter](https://blog.algomaster.io/) 139 | 140 | ## 📺 YouTube Channels 141 | - [Tech Dummies Narendra L](https://www.youtube.com/@TechDummiesNarendraL) 142 | - [Gaurav Sen](https://www.youtube.com/@gkcs) 143 | - [codeKarle](https://www.youtube.com/@codeKarle) 144 | - [ByteByteGo](https://www.youtube.com/@ByteByteGo) 145 | - [System Design Interview](https://www.youtube.com/@SystemDesignInterview) 146 | - [sudoCODE](https://www.youtube.com/@sudocode) 147 | - [Success in Tech](https://www.youtube.com/@SuccessinTech/videos) 148 | 149 | ## 📜 Must-Read Engineering Articles 150 | - [How Discord stores trillions of messages](https://discord.com/blog/how-discord-stores-trillions-of-messages) 151 | - [Building In-Video Search at Netflix](https://netflixtechblog.com/building-in-video-search-936766f0017c) 152 | - [How Canva scaled Media uploads from Zero to 50 Million per Day](https://www.canva.dev/blog/engineering/from-zero-to-50-million-uploads-per-day-scaling-media-at-canva/) 153 | - [How Airbnb avoids double payments in a Distributed Payments System](https://medium.com/airbnb-engineering/avoiding-double-payments-in-a-distributed-payments-system-2981f6b070bb) 154 | - [Stripe’s payments APIs - The first 10 years](https://stripe.com/blog/payment-api-design) 155 | - [Real time messaging at Slack](https://slack.engineering/real-time-messaging/) 156 | 157 | ## 🗞️ Must-Read Distributed Systems Papers 158 | - [Paxos: The Part-Time Parliament](https://lamport.azurewebsites.net/pubs/lamport-paxos.pdf) 159 | - [MapReduce: Simplified Data Processing on Large Clusters](https://research.google.com/archive/mapreduce-osdi04.pdf) 160 | - [The Google File System](https://static.googleusercontent.com/media/research.google.com/en//archive/gfs-sosp2003.pdf) 161 | - [Dynamo: Amazon’s Highly Available Key-value Store](https://www.allthingsdistributed.com/files/amazon-dynamo-sosp2007.pdf) 162 | - [Kafka: a Distributed Messaging System for Log Processing](https://notes.stephenholiday.com/Kafka.pdf) 163 | - [Spanner: Google’s Globally-Distributed Database](https://static.googleusercontent.com/media/research.google.com/en//archive/spanner-osdi2012.pdf) 164 | - [Bigtable: A Distributed Storage System for Structured Data](https://static.googleusercontent.com/media/research.google.com/en//archive/bigtable-osdi06.pdf) 165 | - [ZooKeeper: Wait-free coordination for Internet-scale systems](https://www.usenix.org/legacy/event/usenix10/tech/full_papers/Hunt.pdf) 166 | - [The Log-Structured Merge-Tree (LSM-Tree)](https://www.cs.umb.edu/~poneil/lsmtree.pdf) 167 | - [The Chubby lock service for loosely-coupled distributed systems](https://static.googleusercontent.com/media/research.google.com/en//archive/chubby-osdi06.pdf) 168 | 169 | --- 170 | 171 |

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174 | -------------------------------------------------------------------------------- /diagrams/interview-template.png: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/ashishps1/awesome-system-design-resources/ca2bfbcf3176612614d62d493f8772538a134146/diagrams/interview-template.png -------------------------------------------------------------------------------- /diagrams/system-design-github-logo.png: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/ashishps1/awesome-system-design-resources/ca2bfbcf3176612614d62d493f8772538a134146/diagrams/system-design-github-logo.png -------------------------------------------------------------------------------- /implementations/java/consistent_hashing/ConsistentHashing.java: -------------------------------------------------------------------------------- 1 | package implementations.java.consistent_hashing; 2 | 3 | import java.security.MessageDigest; 4 | import java.security.NoSuchAlgorithmException; 5 | import java.util.*; 6 | 7 | public class ConsistentHashing { 8 | private final int numReplicas; // Number of virtual nodes per server 9 | private final TreeMap ring; // Hash ring storing virtual nodes 10 | private final Set servers; // Set of physical servers 11 | 12 | public ConsistentHashing(List servers, int numReplicas) { 13 | this.numReplicas = numReplicas; 14 | this.ring = new TreeMap<>(); 15 | this.servers = new HashSet<>(); 16 | 17 | // Add each server to the hash ring 18 | for (String server : servers) { 19 | addServer(server); 20 | } 21 | } 22 | 23 | private long hash(String key) { 24 | try { 25 | MessageDigest md = MessageDigest.getInstance("MD5"); 26 | md.update(key.getBytes()); 27 | byte[] digest = md.digest(); 28 | return ((long) (digest[0] & 0xFF) << 24) | 29 | ((long) (digest[1] & 0xFF) << 16) | 30 | ((long) (digest[2] & 0xFF) << 8) | 31 | ((long) (digest[3] & 0xFF)); 32 | } catch (NoSuchAlgorithmException e) { 33 | throw new RuntimeException("MD5 algorithm not found", e); 34 | } 35 | } 36 | 37 | public void addServer(String server) { 38 | servers.add(server); 39 | for (int i = 0; i < numReplicas; i++) { 40 | long hash = hash(server + "-" + i); // Unique hash for each virtual node 41 | ring.put(hash, server); 42 | } 43 | } 44 | 45 | public void removeServer(String server) { 46 | if (servers.remove(server)) { 47 | for (int i = 0; i < numReplicas; i++) { 48 | long hash = hash(server + "-" + i); 49 | ring.remove(hash); 50 | } 51 | } 52 | } 53 | 54 | public String getServer(String key) { 55 | if (ring.isEmpty()) { 56 | return null; // No servers available 57 | } 58 | 59 | long hash = hash(key); 60 | // Find the closest server in a clockwise direction 61 | Map.Entry entry = ring.ceilingEntry(hash); 62 | if (entry == null) { 63 | // If we exceed the highest node, wrap around to the first node 64 | entry = ring.firstEntry(); 65 | } 66 | return entry.getValue(); 67 | } 68 | 69 | public static void main(String[] args) { 70 | List servers = Arrays.asList("S0", "S1", "S2", "S3", "S4", "S5"); 71 | ConsistentHashing ch = new ConsistentHashing(servers, 3); 72 | 73 | // Step 2: Assign requests (keys) to servers 74 | System.out.println("UserA is assigned to: " + ch.getServer("UserA")); 75 | System.out.println("UserB is assigned to: " + ch.getServer("UserB")); 76 | 77 | // Step 3: Add a new server dynamically 78 | ch.addServer("S6"); 79 | System.out.println("UserA is now assigned to: " + ch.getServer("UserA")); 80 | 81 | // Step 4: Remove a server dynamically 82 | ch.removeServer("S2"); 83 | System.out.println("UserB is now assigned to: " + ch.getServer("UserB")); 84 | } 85 | } 86 | 87 | -------------------------------------------------------------------------------- /implementations/java/load_balancing_algorithms/IPHash.java: -------------------------------------------------------------------------------- 1 | import java.util.List; 2 | 3 | public class IPHash { 4 | private List servers; 5 | 6 | public IPHash(List servers) { 7 | this.servers = servers; 8 | } 9 | 10 | public String getNextServer(String clientIp) { 11 | int hash = clientIp.hashCode(); 12 | int serverIndex = Math.abs(hash) % servers.size(); 13 | return servers.get(serverIndex); 14 | } 15 | 16 | public static void main(String[] args) { 17 | List servers = List.of("Server1", "Server2", "Server3"); 18 | IPHash ipHash = new IPHash(servers); 19 | 20 | List clientIps = List.of("192.168.0.1", "192.168.0.2", "192.168.0.3"); 21 | for (String ip : clientIps) { 22 | System.out.println(ip + " is mapped to " + ipHash.getNextServer(ip)); 23 | } 24 | } 25 | } 26 | -------------------------------------------------------------------------------- /implementations/java/load_balancing_algorithms/LeastConnections.java: -------------------------------------------------------------------------------- 1 | import java.util.HashMap; 2 | import java.util.List; 3 | import java.util.Map; 4 | 5 | public class LeastConnections { 6 | private Map serverConnections; 7 | 8 | public LeastConnections(List servers) { 9 | serverConnections = new HashMap<>(); 10 | for (String server : servers) { 11 | serverConnections.put(server, 0); 12 | } 13 | } 14 | 15 | public String getNextServer() { 16 | return serverConnections.entrySet().stream() 17 | .min(Map.Entry.comparingByValue()) 18 | .map(Map.Entry::getKey) 19 | .orElse(null); 20 | } 21 | 22 | public void releaseConnection(String server) { 23 | serverConnections.computeIfPresent(server, (k, v) -> v > 0 ? v - 1 : 0); 24 | } 25 | 26 | public static void main(String[] args) { 27 | List servers = List.of("Server1", "Server2", "Server3"); 28 | LeastConnections leastConnectionsLB = new LeastConnections(servers); 29 | 30 | for (int i = 0; i < 6; i++) { 31 | String server = leastConnectionsLB.getNextServer(); 32 | System.out.println(server); 33 | leastConnectionsLB.releaseConnection(server); 34 | } 35 | } 36 | } 37 | -------------------------------------------------------------------------------- /implementations/java/load_balancing_algorithms/LeastResponseTime.java: -------------------------------------------------------------------------------- 1 | import java.util.ArrayList; 2 | import java.util.List; 3 | import java.util.Random; 4 | 5 | public class LeastResponseTime { 6 | private List servers; 7 | private List responseTimes; 8 | 9 | public LeastResponseTime(List servers) { 10 | this.servers = servers; 11 | this.responseTimes = new ArrayList<>(servers.size()); 12 | for (int i = 0; i < servers.size(); i++) 13 | responseTimes.add(0.0); 14 | } 15 | 16 | public String getNextServer() { 17 | double minResponseTime = responseTimes.get(0); 18 | int minIndex = 0; 19 | for (int i = 1; i < responseTimes.size(); i++) { 20 | if (responseTimes.get(i) < minResponseTime) { 21 | minResponseTime = responseTimes.get(i); 22 | minIndex = i; 23 | } 24 | } 25 | return servers.get(minIndex); 26 | } 27 | 28 | public void updateResponseTime(String server, double responseTime) { 29 | int index = servers.indexOf(server); 30 | responseTimes.set(index, responseTime); 31 | } 32 | 33 | public static double simulateResponseTime(String server) { 34 | // Simulating response time with random delay 35 | Random random = new Random(); 36 | double delay = 0.1 + (1.0 - 0.1) * random.nextDouble(); 37 | try { 38 | Thread.sleep((long) (delay * 1000)); 39 | } catch (InterruptedException e) { 40 | e.printStackTrace(); 41 | } 42 | return delay; 43 | } 44 | 45 | public static void main(String[] args) { 46 | List servers = List.of("Server1", "Server2", "Server3"); 47 | LeastResponseTime leastResponseTimeLB = new LeastResponseTime(servers); 48 | 49 | for (int i = 0; i < 6; i++) { 50 | String server = leastResponseTimeLB.getNextServer(); 51 | System.out.println("Request " + (i + 1) + " -> " + server); 52 | double responseTime = simulateResponseTime(server); 53 | leastResponseTimeLB.updateResponseTime(server, responseTime); 54 | System.out.println("Response Time: " + String.format("%.2f", responseTime) + "s"); 55 | } 56 | 57 | } 58 | } 59 | -------------------------------------------------------------------------------- /implementations/java/load_balancing_algorithms/RoundRobin.java: -------------------------------------------------------------------------------- 1 | import java.util.List; 2 | import java.util.concurrent.atomic.AtomicInteger; 3 | 4 | public class RoundRobin { 5 | private List servers; 6 | private AtomicInteger index; 7 | 8 | public RoundRobin(List servers) { 9 | this.servers = servers; 10 | this.index = new AtomicInteger(-1); 11 | } 12 | 13 | public String getNextServer() { 14 | int currentIndex = index.incrementAndGet() % servers.size(); 15 | return servers.get(currentIndex); 16 | } 17 | 18 | public static void main(String[] args) { 19 | List servers = List.of("Server1", "Server2", "Server3"); 20 | RoundRobin roundRobinLB = new RoundRobin(servers); 21 | 22 | for (int i = 0; i < 6; i++) { 23 | System.out.println(roundRobinLB.getNextServer()); 24 | } 25 | } 26 | } 27 | -------------------------------------------------------------------------------- /implementations/java/load_balancing_algorithms/WeightedRoundRobin.java: -------------------------------------------------------------------------------- 1 | import java.util.List; 2 | 3 | public class WeightedRoundRobin { 4 | private List servers; 5 | private List weights; 6 | private int currentIndex; 7 | private int currentWeight; 8 | 9 | public WeightedRoundRobin(List servers, List weights) { 10 | this.servers = servers; 11 | this.weights = weights; 12 | this.currentIndex = -1; 13 | this.currentWeight = 0; 14 | } 15 | 16 | public String getNextServer() { 17 | while (true) { 18 | currentIndex = (currentIndex + 1) % servers.size(); 19 | if (currentIndex == 0) { 20 | currentWeight--; 21 | if (currentWeight <= 0) { 22 | currentWeight = getMaxWeight(); 23 | } 24 | } 25 | if (weights.get(currentIndex) >= currentWeight) { 26 | return servers.get(currentIndex); 27 | } 28 | } 29 | } 30 | 31 | private int getMaxWeight() { 32 | return weights.stream().max(Integer::compare).orElse(0); 33 | } 34 | 35 | public static void main(String[] args) { 36 | List servers = List.of("Server1", "Server2", "Server3"); 37 | List weights = List.of(5, 1, 1); 38 | WeightedRoundRobin weightedRoundRobinLB = new WeightedRoundRobin(servers, weights); 39 | 40 | for (int i = 0; i < 7; i++) { 41 | System.out.println(weightedRoundRobinLB.getNextServer()); 42 | } 43 | } 44 | } 45 | -------------------------------------------------------------------------------- /implementations/java/rate_limiting/FixedWindowCounter.java: -------------------------------------------------------------------------------- 1 | package implementations.java.rate_limiting; 2 | 3 | import java.time.Instant; 4 | 5 | public class FixedWindowCounter { 6 | private final long windowSizeInSeconds; // Size of each window in seconds 7 | private final long maxRequestsPerWindow; // Maximum number of requests allowed per window 8 | private long currentWindowStart; // Start time of the current window 9 | private long requestCount; // Number of requests in the current window 10 | 11 | public FixedWindowCounter(long windowSizeInSeconds, long maxRequestsPerWindow) { 12 | this.windowSizeInSeconds = windowSizeInSeconds; 13 | this.maxRequestsPerWindow = maxRequestsPerWindow; 14 | this.currentWindowStart = Instant.now().getEpochSecond(); 15 | this.requestCount = 0; 16 | } 17 | 18 | public synchronized boolean allowRequest() { 19 | long now = Instant.now().getEpochSecond(); 20 | 21 | // Check if we've moved to a new window 22 | if (now - currentWindowStart >= windowSizeInSeconds) { 23 | currentWindowStart = now; // Start a new window 24 | requestCount = 0; // Reset the count for the new window 25 | } 26 | 27 | if (requestCount < maxRequestsPerWindow) { 28 | requestCount++; // Increment the count for this window 29 | return true; // Allow the request 30 | } 31 | return false; // We've exceeded the limit for this window, deny the request 32 | } 33 | } 34 | -------------------------------------------------------------------------------- /implementations/java/rate_limiting/LeakyBucket.java: -------------------------------------------------------------------------------- 1 | package implementations.java.rate_limiting; 2 | 3 | import java.time.Instant; 4 | import java.util.LinkedList; 5 | import java.util.Queue; 6 | 7 | public class LeakyBucket { 8 | private final long capacity; // Maximum number of requests the bucket can hold 9 | private final double leakRate; // Rate at which requests leak out of the bucket (requests per second) 10 | private final Queue bucket; // Queue to hold timestamps of requests 11 | private Instant lastLeakTimestamp; // Last time we leaked from the bucket 12 | 13 | public LeakyBucket(long capacity, double leakRate) { 14 | this.capacity = capacity; 15 | this.leakRate = leakRate; 16 | this.bucket = new LinkedList<>(); 17 | this.lastLeakTimestamp = Instant.now(); 18 | } 19 | 20 | public synchronized boolean allowRequest() { 21 | leak(); // First, leak out any requests based on elapsed time 22 | 23 | if (bucket.size() < capacity) { 24 | bucket.offer(Instant.now()); // Add the new request to the bucket 25 | return true; // Allow the request 26 | } 27 | return false; // Bucket is full, deny the request 28 | } 29 | 30 | private void leak() { 31 | Instant now = Instant.now(); 32 | long elapsedMillis = now.toEpochMilli() - lastLeakTimestamp.toEpochMilli(); 33 | int leakedItems = (int) (elapsedMillis * leakRate / 1000.0); // Calculate how many items should have leaked 34 | 35 | // Remove the leaked items from the bucket 36 | for (int i = 0; i < leakedItems && !bucket.isEmpty(); i++) { 37 | bucket.poll(); 38 | } 39 | 40 | lastLeakTimestamp = now; 41 | } 42 | } 43 | -------------------------------------------------------------------------------- /implementations/java/rate_limiting/SlidingWindowCounter.java: -------------------------------------------------------------------------------- 1 | package implementations.java.rate_limiting; 2 | 3 | import java.time.Instant; 4 | 5 | public class SlidingWindowCounter { 6 | private final long windowSizeInSeconds; // Size of the sliding window in seconds 7 | private final long maxRequestsPerWindow; // Maximum number of requests allowed in the window 8 | private long currentWindowStart; // Start time of the current window 9 | private long previousWindowCount; // Number of requests in the previous window 10 | private long currentWindowCount; // Number of requests in the current window 11 | 12 | public SlidingWindowCounter(long windowSizeInSeconds, long maxRequestsPerWindow) { 13 | this.windowSizeInSeconds = windowSizeInSeconds; 14 | this.maxRequestsPerWindow = maxRequestsPerWindow; 15 | this.currentWindowStart = Instant.now().getEpochSecond(); 16 | this.previousWindowCount = 0; 17 | this.currentWindowCount = 0; 18 | } 19 | 20 | public synchronized boolean allowRequest() { 21 | long now = Instant.now().getEpochSecond(); 22 | long timePassedInWindow = now - currentWindowStart; 23 | 24 | // Check if we've moved to a new window 25 | if (timePassedInWindow >= windowSizeInSeconds) { 26 | previousWindowCount = currentWindowCount; 27 | currentWindowCount = 0; 28 | currentWindowStart = now; 29 | timePassedInWindow = 0; 30 | } 31 | 32 | // Calculate the weighted count of requests 33 | double weightedCount = previousWindowCount * ((windowSizeInSeconds - timePassedInWindow) / (double) windowSizeInSeconds) 34 | + currentWindowCount; 35 | 36 | if (weightedCount < maxRequestsPerWindow) { 37 | currentWindowCount++; // Increment the count for this window 38 | return true; // Allow the request 39 | } 40 | return false; // We've exceeded the limit, deny the request 41 | } 42 | } 43 | -------------------------------------------------------------------------------- /implementations/java/rate_limiting/SlidingWindowLog.java: -------------------------------------------------------------------------------- 1 | package implementations.java.rate_limiting; 2 | 3 | import java.time.Instant; 4 | import java.util.LinkedList; 5 | import java.util.Queue; 6 | 7 | public class SlidingWindowLog { 8 | private final long windowSizeInSeconds; // Size of the sliding window in seconds 9 | private final long maxRequestsPerWindow; // Maximum number of requests allowed in the window 10 | private final Queue requestLog; // Log of request timestamps 11 | 12 | public SlidingWindowLog(long windowSizeInSeconds, long maxRequestsPerWindow) { 13 | this.windowSizeInSeconds = windowSizeInSeconds; 14 | this.maxRequestsPerWindow = maxRequestsPerWindow; 15 | this.requestLog = new LinkedList<>(); 16 | } 17 | 18 | public synchronized boolean allowRequest() { 19 | long now = Instant.now().getEpochSecond(); 20 | long windowStart = now - windowSizeInSeconds; 21 | 22 | // Remove timestamps that are outside of the current window 23 | while (!requestLog.isEmpty() && requestLog.peek() <= windowStart) { 24 | requestLog.poll(); 25 | } 26 | 27 | if (requestLog.size() < maxRequestsPerWindow) { 28 | requestLog.offer(now); // Log this request 29 | return true; // Allow the request 30 | } 31 | return false; // We've exceeded the limit for this window, deny the request 32 | } 33 | } 34 | -------------------------------------------------------------------------------- /implementations/java/rate_limiting/TokenBucket.java: -------------------------------------------------------------------------------- 1 | package implementations.java.rate_limiting; 2 | 3 | import java.time.Instant; 4 | 5 | public class TokenBucket { 6 | private final long capacity; // Maximum number of tokens the bucket can hold 7 | private final double fillRate; // Rate at which tokens are added to the bucket (tokens per second) 8 | private double tokens; // Current number of tokens in the bucket 9 | private Instant lastRefillTimestamp; // Last time we refilled the bucket 10 | 11 | public TokenBucket(long capacity, double fillRate) { 12 | this.capacity = capacity; 13 | this.fillRate = fillRate; 14 | this.tokens = capacity; // Start with a full bucket 15 | this.lastRefillTimestamp = Instant.now(); 16 | } 17 | 18 | public synchronized boolean allowRequest(int tokens) { 19 | refill(); // First, add any new tokens based on elapsed time 20 | 21 | if (this.tokens < tokens) { 22 | return false; // Not enough tokens, deny the request 23 | } 24 | 25 | this.tokens -= tokens; // Consume the tokens 26 | return true; // Allow the request 27 | } 28 | 29 | private void refill() { 30 | Instant now = Instant.now(); 31 | // Calculate how many tokens to add based on the time elapsed 32 | double tokensToAdd = (now.toEpochMilli() - lastRefillTimestamp.toEpochMilli()) * fillRate / 1000.0; 33 | this.tokens = Math.min(capacity, this.tokens + tokensToAdd); // Add tokens, but don't exceed capacity 34 | this.lastRefillTimestamp = now; 35 | } 36 | } -------------------------------------------------------------------------------- /implementations/python/consistent_hashing/consistent-hashing.py: -------------------------------------------------------------------------------- 1 | import hashlib 2 | import bisect 3 | 4 | class ConsistentHashing: 5 | def __init__(self, servers, num_replicas=3): 6 | """ 7 | Initializes the consistent hashing ring. 8 | 9 | - servers: List of initial server names (e.g., ["S0", "S1", "S2"]) 10 | - num_replicas: Number of virtual nodes per server for better load balancing 11 | """ 12 | self.num_replicas = num_replicas # Number of virtual nodes per server 13 | self.ring = {} # Hash ring storing virtual node mappings 14 | self.sorted_keys = [] # Sorted list of hash values (positions) on the ring 15 | self.servers = set() # Set of physical servers (used for tracking) 16 | 17 | # Add each server to the hash ring 18 | for server in servers: 19 | self.add_server(server) 20 | 21 | def _hash(self, key): 22 | """Computes a hash value for a given key using MD5.""" 23 | return int(hashlib.md5(key.encode()).hexdigest(), 16) 24 | 25 | def add_server(self, server): 26 | """ 27 | Adds a server to the hash ring along with its virtual nodes. 28 | 29 | - Each virtual node is a different hash of the server ID to distribute load. 30 | - The server is hashed multiple times and placed at different positions. 31 | """ 32 | self.servers.add(server) 33 | for i in range(self.num_replicas): # Creating multiple virtual nodes 34 | hash_val = self._hash(f"{server}-{i}") # Unique hash for each virtual node 35 | self.ring[hash_val] = server # Map hash to the server 36 | bisect.insort(self.sorted_keys, hash_val) # Maintain a sorted list for efficient lookup 37 | 38 | def remove_server(self, server): 39 | """ 40 | Removes a server and all its virtual nodes from the hash ring. 41 | """ 42 | if server in self.servers: 43 | self.servers.remove(server) 44 | for i in range(self.num_replicas): 45 | hash_val = self._hash(f"{server}-{i}") # Remove each virtual node's hash 46 | self.ring.pop(hash_val, None) # Delete from hash ring 47 | self.sorted_keys.remove(hash_val) # Remove from sorted key list 48 | 49 | def get_server(self, key): 50 | """ 51 | Finds the closest server for a given key. 52 | 53 | - Hash the key to get its position on the ring. 54 | - Move clockwise to find the nearest server. 55 | - If it exceeds the last node, wrap around to the first node. 56 | """ 57 | if not self.ring: 58 | return None # No servers available 59 | 60 | hash_val = self._hash(key) # Hash the key 61 | index = bisect.bisect(self.sorted_keys, hash_val) % len(self.sorted_keys) # Locate nearest server 62 | return self.ring[self.sorted_keys[index]] # Return the assigned server 63 | 64 | # ----------------- Usage Example ------------------- 65 | 66 | # Step 1: Initialize Consistent Hashing with servers 67 | servers = ["S0", "S1", "S2", "S3", "S4", "S5"] 68 | ch = ConsistentHashing(servers) 69 | 70 | # Step 2: Assign requests (keys) to servers 71 | print(ch.get_server("UserA")) # Maps UserA to a server 72 | print(ch.get_server("UserB")) # Maps UserB to a server 73 | 74 | # Step 3: Add a new server dynamically 75 | ch.add_server("S6") 76 | print(ch.get_server("UserA")) # Might be reassigned if affected 77 | 78 | # Step 4: Remove a server dynamically 79 | ch.remove_server("S2") 80 | print(ch.get_server("UserB")) # Might be reassigned if affected -------------------------------------------------------------------------------- /implementations/python/load_balancing_algorithms/ip_hash.py: -------------------------------------------------------------------------------- 1 | import hashlib 2 | 3 | class IPHash(): 4 | def __init__(self, servers): 5 | self.servers = servers 6 | 7 | def get_next_server(self, client_ip): 8 | hash_value = hashlib.md5(client_ip.encode()).hexdigest() 9 | index = int(hash_value, 16) % len(self.servers) 10 | return self.servers[index] 11 | 12 | # Example usage 13 | servers = ["Server1", "Server2", "Server3"] 14 | load_balancer = IPHash(servers) 15 | 16 | client_ips = ["192.168.0.1", "192.168.0.2", "192.168.0.3", "192.168.0.4"] 17 | for ip in client_ips: 18 | server = load_balancer.get_next_server(ip) 19 | print(f"Client {ip} -> {server}") -------------------------------------------------------------------------------- /implementations/python/load_balancing_algorithms/least_connections.py: -------------------------------------------------------------------------------- 1 | import random 2 | 3 | class LeastConnections: 4 | def __init__(self, servers): 5 | self.servers = {server: 0 for server in servers} 6 | 7 | def get_next_server(self): 8 | # Find the minimum number of connections 9 | min_connections = min(self.servers.values()) 10 | # Get all servers with the minimum number of connections 11 | least_loaded_servers = [server for server, connections in self.servers.items() if connections == min_connections] 12 | # Select a random server from the least loaded servers 13 | selected_server = random.choice(least_loaded_servers) 14 | self.servers[selected_server] += 1 15 | return selected_server 16 | 17 | def release_connection(self, server): 18 | if self.servers[server] > 0: 19 | self.servers[server] -= 1 20 | 21 | # Example usage 22 | servers = ["Server1", "Server2", "Server3"] 23 | load_balancer = LeastConnections(servers) 24 | 25 | for i in range(6): 26 | server = load_balancer.get_next_server() 27 | print(f"Request {i + 1} -> {server}") 28 | load_balancer.release_connection(server) -------------------------------------------------------------------------------- /implementations/python/load_balancing_algorithms/least_response_time.py: -------------------------------------------------------------------------------- 1 | import time 2 | import random 3 | 4 | class LeastResponseTime: 5 | def __init__(self, servers): 6 | self.servers = servers 7 | self.response_times = [0] * len(servers) 8 | 9 | def get_next_server(self): 10 | min_response_time = min(self.response_times) 11 | min_index = self.response_times.index(min_response_time) 12 | return self.servers[min_index] 13 | 14 | def update_response_time(self, server, response_time): 15 | index = self.servers.index(server) 16 | self.response_times[index] = response_time 17 | 18 | # Simulated server response time function 19 | def simulate_response_time(): 20 | # Simulating response time with random delay 21 | delay = random.uniform(0.1, 1.0) 22 | time.sleep(delay) 23 | return delay 24 | 25 | # Example usage 26 | servers = ["Server1", "Server2", "Server3"] 27 | load_balancer = LeastResponseTime(servers) 28 | 29 | for i in range(6): 30 | server = load_balancer.get_next_server() 31 | print(f"Request {i + 1} -> {server}") 32 | response_time = simulate_response_time() 33 | load_balancer.update_response_time(server, response_time) 34 | print(f"Response Time: {response_time:.2f}s") -------------------------------------------------------------------------------- /implementations/python/load_balancing_algorithms/round_robin.py.py: -------------------------------------------------------------------------------- 1 | class RoundRobin: 2 | def __init__(self, servers): 3 | self.servers = servers 4 | self.current_index = -1 5 | 6 | def get_next_server(self): 7 | self.current_index = (self.current_index + 1) % len(self.servers) 8 | return self.servers[self.current_index] 9 | 10 | # Example usage 11 | servers = ["Server1", "Server2", "Server3"] 12 | load_balancer = RoundRobin(servers) 13 | 14 | for i in range(6): 15 | server = load_balancer.get_next_server() 16 | print(f"Request {i + 1} -> {server}") -------------------------------------------------------------------------------- /implementations/python/load_balancing_algorithms/weighted_round_robin.py: -------------------------------------------------------------------------------- 1 | class WeightedRoundRobin: 2 | def __init__(self, servers, weights): 3 | self.servers = servers 4 | self.weights = weights 5 | self.current_index = -1 6 | self.current_weight = 0 7 | 8 | def get_next_server(self): 9 | while True: 10 | self.current_index = (self.current_index + 1) % len(self.servers) 11 | if self.current_index == 0: 12 | self.current_weight -= 1 13 | if self.current_weight <= 0: 14 | self.current_weight = max(self.weights) 15 | if self.weights[self.current_index] >= self.current_weight: 16 | return self.servers[self.current_index] 17 | 18 | # Example usage 19 | servers = ["Server1", "Server2", "Server3"] 20 | weights = [5, 1, 1] 21 | load_balancer = WeightedRoundRobin(servers, weights) 22 | 23 | for i in range(7): 24 | server = load_balancer.get_next_server() 25 | print(f"Request {i + 1} -> {server}") -------------------------------------------------------------------------------- /implementations/python/rate_limiting/fixed_window_counter.py: -------------------------------------------------------------------------------- 1 | import time 2 | 3 | class FixedWindowCounter: 4 | def __init__(self, window_size, max_requests): 5 | self.window_size = window_size # Size of the window in seconds 6 | self.max_requests = max_requests # Maximum number of requests per window 7 | self.current_window = time.time() // window_size 8 | self.request_count = 0 9 | 10 | def allow_request(self): 11 | current_time = time.time() 12 | window = current_time // self.window_size 13 | 14 | # If we've moved to a new window, reset the counter 15 | if window != self.current_window: 16 | self.current_window = window 17 | self.request_count = 0 18 | 19 | # Check if we're still within the limit for this window 20 | if self.request_count < self.max_requests: 21 | self.request_count += 1 22 | return True 23 | return False 24 | 25 | # Usage example 26 | limiter = FixedWindowCounter(window_size=60, max_requests=5) # 5 requests per minute 27 | 28 | for _ in range(10): 29 | print(limiter.allow_request()) # Will print True for the first 5 requests, then False 30 | time.sleep(0.1) # Wait a bit between requests 31 | 32 | time.sleep(60) # Wait for the window to reset 33 | print(limiter.allow_request()) # True -------------------------------------------------------------------------------- /implementations/python/rate_limiting/leaky_bucket.py: -------------------------------------------------------------------------------- 1 | from collections import deque 2 | import time 3 | 4 | class LeakyBucket: 5 | def __init__(self, capacity, leak_rate): 6 | self.capacity = capacity # Maximum number of requests in the bucket 7 | self.leak_rate = leak_rate # Rate at which requests leak (requests/second) 8 | self.bucket = deque() # Queue to hold request timestamps 9 | self.last_leak = time.time() # Last time we leaked from the bucket 10 | 11 | def allow_request(self): 12 | now = time.time() 13 | # Simulate leaking from the bucket 14 | leak_time = now - self.last_leak 15 | leaked = int(leak_time * self.leak_rate) 16 | if leaked > 0: 17 | # Remove the leaked requests from the bucket 18 | for _ in range(min(leaked, len(self.bucket))): 19 | self.bucket.popleft() 20 | self.last_leak = now 21 | 22 | # Check if there's capacity and add the new request 23 | if len(self.bucket) < self.capacity: 24 | self.bucket.append(now) 25 | return True 26 | return False 27 | 28 | # Usage example 29 | limiter = LeakyBucket(capacity=5, leak_rate=1) # 5 requests, leak 1 per second 30 | 31 | for _ in range(10): 32 | print(limiter.allow_request()) # Will print True for the first 5 requests, then False 33 | time.sleep(0.1) # Wait a bit between requests 34 | 35 | time.sleep(1) # Wait for bucket to leak 36 | print(limiter.allow_request()) # True -------------------------------------------------------------------------------- /implementations/python/rate_limiting/sliding_window_counter.py: -------------------------------------------------------------------------------- 1 | import time 2 | 3 | class SlidingWindowCounter: 4 | def __init__(self, window_size, max_requests): 5 | self.window_size = window_size # Size of the sliding window in seconds 6 | self.max_requests = max_requests # Maximum number of requests per window 7 | self.current_window = time.time() // window_size 8 | self.request_count = 0 9 | self.previous_count = 0 10 | 11 | def allow_request(self): 12 | now = time.time() 13 | window = now // self.window_size 14 | 15 | # If we've moved to a new window, update the counts 16 | if window != self.current_window: 17 | self.previous_count = self.request_count 18 | self.request_count = 0 19 | self.current_window = window 20 | 21 | # Calculate the weighted request count 22 | window_elapsed = (now % self.window_size) / self.window_size 23 | threshold = self.previous_count * (1 - window_elapsed) + self.request_count 24 | 25 | # Check if we're within the limit 26 | if threshold < self.max_requests: 27 | self.request_count += 1 28 | return True 29 | return False 30 | 31 | # Usage example 32 | limiter = SlidingWindowCounter(window_size=60, max_requests=5) # 5 requests per minute 33 | 34 | for _ in range(10): 35 | print(limiter.allow_request()) # Will print True for the first 5 requests, then gradually become False 36 | time.sleep(0.1) # Wait a bit between requests 37 | 38 | time.sleep(30) # Wait for half the window to pass 39 | print(limiter.allow_request()) # Might be True or False depending on the exact timing -------------------------------------------------------------------------------- /implementations/python/rate_limiting/sliding_window_log.py: -------------------------------------------------------------------------------- 1 | import time 2 | from collections import deque 3 | 4 | class SlidingWindowLog: 5 | def __init__(self, window_size, max_requests): 6 | self.window_size = window_size # Size of the sliding window in seconds 7 | self.max_requests = max_requests # Maximum number of requests per window 8 | self.request_log = deque() # Log to keep track of request timestamps 9 | 10 | def allow_request(self): 11 | now = time.time() 12 | 13 | # Remove timestamps that are outside the current window 14 | while self.request_log and now - self.request_log[0] >= self.window_size: 15 | self.request_log.popleft() 16 | 17 | # Check if we're still within the limit 18 | if len(self.request_log) < self.max_requests: 19 | self.request_log.append(now) 20 | return True 21 | return False 22 | 23 | # Usage example 24 | limiter = SlidingWindowLog(window_size=60, max_requests=5) # 5 requests per minute 25 | 26 | for _ in range(10): 27 | print(limiter.allow_request()) # Will print True for the first 5 requests, then False 28 | time.sleep(0.1) # Wait a bit between requests 29 | 30 | time.sleep(60) # Wait for the window to slide 31 | print(limiter.allow_request()) # True -------------------------------------------------------------------------------- /implementations/python/rate_limiting/token_bucket.py: -------------------------------------------------------------------------------- 1 | import time 2 | 3 | class TokenBucket: 4 | def __init__(self, capacity, fill_rate): 5 | self.capacity = capacity # Maximum number of tokens the bucket can hold 6 | self.fill_rate = fill_rate # Rate at which tokens are added (tokens/second) 7 | self.tokens = capacity # Current token count, start with a full bucket 8 | self.last_time = time.time() # Last time we checked the token count 9 | 10 | def allow_request(self, tokens=1): 11 | now = time.time() 12 | # Calculate how many tokens have been added since the last check 13 | time_passed = now - self.last_time 14 | self.tokens = min(self.capacity, self.tokens + time_passed * self.fill_rate) 15 | self.last_time = now 16 | 17 | # Check if we have enough tokens for this request 18 | if self.tokens >= tokens: 19 | self.tokens -= tokens 20 | return True 21 | return False 22 | 23 | # Usage example 24 | limiter = TokenBucket(capacity=10, fill_rate=1) # 10 tokens, refill 1 token per second 25 | 26 | for _ in range(15): 27 | print(limiter.allow_request()) # Will print True for the first 10 requests, then False 28 | time.sleep(0.1) # Wait a bit between requests 29 | 30 | time.sleep(5) # Wait for bucket to refill 31 | print(limiter.allow_request()) # True --------------------------------------------------------------------------------