Distributed Systems Architecture

Consistent Hashing

A distributed hashing technique that maps both server nodes and keys to a logical circular hash ring, ensuring that adding or removing a node requires remapping only K/N keys.

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Deep Dive

How Consistent Hashing Works in Production

Under-the-hood mechanics and technical implementation details.

Technical Deep Dive

Detailed Architecture

In traditional modulo hashing (hash(key) % N), changing the number of nodes N causes nearly all keys to remap, triggering disastrous cache stampedes. Consistent hashing maps nodes and keys onto a 360-degree ring (0 to 2^32 - 1). A key is assigned to the first server node encountered in clockwise direction. By adding virtual nodes (e.g. 100-250 virtual tokens per physical node), key distribution is balanced evenly across heterogeneous hardware.

Key Architectural Rule / Formula:

Keys Remapped on Node Change = Total Keys (K) / Number of Servers (N)

Engineering Trade-Offs

Trade-Off Dimensions & Analysis

Evaluating advantages and drawbacks during architecture interviews.

Dimension	Advantages (Pros)	Drawbacks & Costs (Cons)
Key Rebalancing	Only K/N keys are moved when nodes join or leave, preventing cache invalidation storms.	Requires maintaining a sorted hash ring structure (O(log N) lookup using binary search).
Virtual Nodes	Eliminates non-uniform data skew and hot spots across physical servers.	Increases metadata memory footprint and ring synchronization complexity.

Interview Application

How to Frame Consistent Hashing in System Design Rounds

Senior-level talking points and related interview problems.

Interview Strategy

Evaluating in Loops

Frequently tested in distributed cache design (Memcached/Redis clusters), distributed databases (DynamoDB, Cassandra), and load balancer routing.

Applied System Design Scenarios

Distributed Cache (Memcached/Redis)
Distributed Key-Value Store
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