Design Distributed Cache
Last Updated: December 29, 2025
What is a Distributed Cache?
A distributed cache is a caching system that stores data across multiple servers, allowing applications to retrieve frequently accessed data much faster than querying a primary database.
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The core idea is to reduce latency and database load by keeping "hot" data in memory, spread across a cluster of cache nodes that can scale horizontally. Unlike a single-server cache, a distributed cache can handle massive amounts of data and traffic by adding more nodes to the cluster.
Popular Examples: Redis, Memcached, Amazon ElastiCache, Hazelcast
This problem touches on many fundamental system design concepts: data partitioning, consistency vs availability trade-offs, failure handling, and cache invalidation (famously one of the two hard problems in computer science).
In this chapter, we will explore the high-level design of a distributed cache.
Let's start by clarifying the requirements: