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Day 24: Consistent Hashing for Balanced Log Distribution
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Day 24: Consistent Hashing for Balanced Log Distribution

254-Day Hands-On System Design Series

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System Design Course
Jun 04, 2025
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Day 24: Consistent Hashing for Balanced Log Distribution
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From chaos to harmony: How Netflix and Amazon solve the "hot potato" problem of distributed storage


🎯 Learning Objectives

By the end of this lesson, you will understand how consistent hashing solves the fundamental problem of distributing data across multiple servers while minimizing disruption during scaling operations. You'll implement a production-ready consistent hashing system that forms the backbone of many distributed systems used by companies like Amazon, Netflix, and LinkedIn.

What You'll Build:

  • ⚡ High-performance hash ring with virtual nodes (50K+ lookups/sec)

  • 🔄 Dynamic cluster scaling with minimal data movement (25% vs 100%)

  • 📊 Real-time monitoring dashboard with load visualization

  • 🧪 Comprehensive test suite validating correctness and performance


🚨 The Problem That Keeps Engineers Awake

Picture this: You're running a popular social media app, and suddenly one of your storage servers is drowning in log data while others sit nearly empty. Your users from New York are experiencing slow response times because their logs happened to hash to the overloaded server, while users from smaller cities enjoy lightning-fast performance. This is the classic "hot spot" problem that simple hash-based distribution creates.

Traditional hashing seems logical at first. Take a log entry, compute hash(log_id) % number_of_servers, and store it there. This works beautifully until you need to add or remove servers. Suddenly, almost every log needs to move to a different server, causing massive data reshuffling that can bring your system to its knees.

Think of it like having assigned lockers in a school hallway. When the school adds a new wing with more lockers, you don't want every student to change their locker assignment. You want minimal disruption with maximum balance.


💡 Consistent Hashing: The Elegant Solution

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