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The third post in a series on distributed systems through the MIT 6.5840 labs. This post walks through implementing Raft's leader election mechanism — the foundation of a fault-tolerant distributed system. [Read More]

When you add or remove a server in a distributed cache, traditional hashing forces nearly every key to move to a different server — causing cache storms and cascading failures. Consistent hashing solves this elegantly. Here's how it works, and how it powers DynamoDB, Cassandra, Akamai, and Google's own load... [Read More]

Rate limiting is one of those problems that sounds simple until you try to build it at scale. Five algorithms, each with real trade-offs. Distributed challenges like race conditions and sync. Here's how to think through all of it. [Read More]

How to design a payment backend for e-commerce: pay-in and pay-out, using a payment provider (PSP), double-entry bookkeeping, hosted payment pages, and how to avoid double charges when things fail or users click Pay twice. [Read More]

A comprehensive guide to designing a real-time gaming leaderboard: from clarifying requirements and back-of-the-envelope estimation to Redis Sorted Sets, a seven-step event-driven pipeline (Kafka, throttle, checksum, WebSocket), scaling with sharding, tie-breaking, and recovery. [Read More]

Designing a scalable hotel booking system at scale. Learn about inventory management, concurrency control, distributed transactions, and how to handle hundreds of thousands of bookings per day with data integrity and fault tolerance. [Read More]

Designing an ad click event aggregation system at Facebook or Google scale. Learn about real-time bidding, stream processing, exactly-once semantics, and how to handle billions of clicks per day with proper fault tolerance and data accuracy. [Read More]

How do services like Dropbox and Google Drive store petabytes of data while keeping files synchronized across millions of devices in real-time? In this comprehensive deep dive, I explore the architecture behind a scalable cloud file storage service, covering chunking strategies, synchronization mechanisms, and database scaling techniques. [Read More]

Ever wondered how messaging apps like WhatsApp or Telegram handle billions of messages daily while maintaining instant delivery and end-to-end encryption? In this deep dive, I explore the architecture behind a scalable real-time chat application, covering everything from WebSocket connections to message routing and E2EE security. [Read More]

How do music streaming services like Spotify handle millions of users streaming billions of songs? In this comprehensive system design deep dive, we'll explore scalable architecture, capacity planning, data storage strategies, and the technologies that power modern music platforms. [Read More]