Microsoft LLD – Design Multi-API & Combined Rate Limiter

Description

🚀 Design Multi-API & Combined Rate Limiter (Asked in Microsoft) Rate limiting is one of the most important components in building scalable backend systems. In real-world production systems, simple rate limiting is often not enough. Systems must support different limits for different APIs, multiple time windows, and combined limits across multiple endpoints. In this video, we design a thread-safe, extensible Rate Limiting Library in Java that supports advanced production-level requirements. 🔹 Problem We Solve Design a rate limiter that supports: 1️⃣ Granular API Limits Different APIs have different limits. Example: /login → 5 requests per minute /search → 100 requests per minute 2️⃣ Multi-Period Constraints Same API can have multiple limits at different time windows. Example: 10 requests per minute 500 requests per day 3️⃣ Combined / Aggregate Limits Rate limits applied to a group of APIs together. Example: /upload + /download together → max 50 requests per hour 4️⃣ Algorithm Flexibility Support multiple rate limiting algorithms: Token Bucket Sliding Window Leaky Bucket Fixed Window 5️⃣ Low Latency + Thread Safety Designed for high concurrency backend systems with safe and fast decision making. 🎯 Key Components Covered ✔ PeriodLimit (multi-window rate limits) ✔ EndpointRule (per API rules) ✔ AggregateRule (group-level limits) ✔ BucketFactory (strategy pattern for algorithms) ✔ CombinedRateLimiter (core rate limiter engine) ✔ Token Bucket implementation ✔ Sliding Window implementation ✔ Leaky Bucket implementation ✔ Fixed Window implementation 🧠 Concepts You Will Learn • Real-world API rate limiting strategies • Designing extensible libraries in Java • Strategy Pattern for algorithm selection • Thread-safe concurrent design • Handling multi-window rate limits • Aggregated API quotas • Production-ready system design thinking 💻 Who Should Watch This video is perfect for: • Backend Engineers • Java Developers • System Design Learners • Engineers preparing for LLD / Machine Coding Interviews Companies where similar questions are asked include Amazon, Microsoft, Walmart, PhonePe, PayPal, and Salesforce. 📌 Real Interview Preparation If you want to get strong at Low Level Design interviews, problems like this help you understand: • Writing clean object-oriented design • Handling concurrency • Designing reusable libraries • Implementing scalable backend components 👍 If you found this useful, Like, Share & Subscribe for more System Design, LLD, and Backend Engineering content. #SystemDesign #LowLevelDesign #RateLimiter #JavaBackend #MachineCoding #SoftwareEngineering #BackendDevelopment