Redis
An in-memory data store used as a cache, message broker, and database. Blazing fast because everything lives in RAM.
What is Redis?
An in-memory data store used as a cache, message broker, and database. Blazing fast because everything lives in RAM.
Redis is a intermediate-level concept that sits in the Database Types & Storage area of system design. Engineers reach for it whenever they need to reason about real-world trade-offs in that space — not just for textbook correctness, but because real production systems at companies like Netflix, Amazon, and Google make these decisions every day.
If you want to go deeper than this definition — with diagrams, code, and a quiz to lock it in — work through the "Redis" lesson linked below. It walks through the why, the mechanism, the trade-offs, and how the giants actually use it in production.
Learn Redis in depth
Full interactive lesson with diagrams, code examples, real-world references, and a quiz.
Open the Redis lessonRelated lessons
Lessons that touch on Redis as part of a larger topic.
Redis Cache
The Swiss Army knife of caching, data structures, persistence, clustering, and why nearly every major tech company runs Redis
foundation · caching strategies
Application-Level Caching
Distributed caching with Redis and Memcached, the shared brain across your servers
foundation · caching strategies
Snapshotting
Capture a consistent point-in-time view of distributed state without stopping the system
advanced · consistency models
Design a Rate Limiter
Design a distributed rate limiting system - token bucket, sliding window, and protecting services at massive scale
capstone · capstone
Remote Cache
A shared cache that lives on a separate server, trade local speed for cross-instance consistency
foundation · caching strategies
See also
Related glossary terms you might want to look up next.
Memcached
A simple, high-performance distributed memory caching system. Stores key-value pairs in RAM. Simpler than Redis but less feature-rich.
Caching
Storing frequently accessed data in a faster storage layer so you don't have to fetch it from the original (slower) source every time.
Rate Limiting
Controlling how many requests a client can make in a given time window. Protects your API from abuse and ensures fair usage.