Redis Implementation Guides

Redis is more than a cache. Its versatile data structures and atomic operations make it ideal for implementing common distributed system primitives like rate limiters, locks, queues, and counters. These patterns appear everywhere in production systems but are often implemented incorrectly or inefficiently.

This section provides practical guides for implementing these primitives with Redis. Each guide covers multiple approaches, explains the tradeoffs, and includes working code examples you can adapt for your own systems.

📄️How to Implement Rate Limiting in Redis

Implement rate limiting in Redis with four algorithms, fixed window, sliding window, token bucket, and leaky bucket, and when to use each.

📄️How to Build a Scheduled Queue in Redis

Build a scheduled queue in Redis with sorted sets, scheduling tasks by timestamp and claiming them atomically for multi-worker setups.

📄️How to Build a URL Shortener in Redis

Build a URL shortener in Redis using string lookups and base62 counter codes, with click tracking and analytics via counters and sorted sets.

📄️How to Build a Distributed Lock in Redis

Build a distributed lock in Redis with SET NX, automatic expiration to prevent deadlocks, and lock extension for long-running operations.

📄️How to Build Feature Flags in Redis

Build feature flags in Redis, from global on/off toggles to percentage-based rollouts and user targeting, with working code examples.

📄️How to Track Online Users in Redis

Track online users in Redis with sorted sets, covering site-wide presence, per-room tracking, and rich status metadata, with code examples.

📄️How to Store User Sessions in Redis

Store user sessions in Redis with serialized strings or hashes, plus sliding expiration to keep active sessions alive across app servers.

📄️How to Process Jobs Exactly Once in Redis

Process jobs exactly once in Redis using job ID deduplication, atomic claims, and idempotency keys to prevent duplicate charges and emails.

📄️How to Build Typing Indicators in Redis

Build typing indicators in Redis with expiring keys, sorted sets for group chats, and Pub/Sub for real-time updates, with code examples.

📄️How to Count Unique Users Without Storing Every ID

Count unique visitors in Redis with Sets for exact counts or HyperLogLog for approximate counts in 12KB of memory, whatever your traffic.

📄️How to Check if a Value Exists Without Storing It

Check if a value exists without storing it using Redis Bloom filters, with memory-efficient probabilistic checks compared against exact Sets.

📄️How to Build a Reliable Queue in Redis

Build a reliable queue in Redis using LMOVE, a processing list, and a recovery process so jobs survive worker crashes with at-least-once delivery.