Redis Essentials: Caching, Queues & Real-Time Data

What Is Redis and When to Use It

An in-memory key-value data store: why it is so fast, what it is used for, and what it should not replace.

Setting Up Redis & redis-cli

Run Redis with Docker, WSL or a free cloud database, and connect with redis-cli and Redis Insight.

Keys, Strings, Counters & Expiry

Name keys well, store strings, count with INCR, and make data disappear automatically with TTLs.

Hashes: Objects in One Key

Store objects like a user profile or cart as hashes and update individual fields.

Lists: Queues & Recent Items

Push and pop from both ends, keep "latest N" lists, and build simple queues.

Sets: Unique Members & Set Maths

Track unique items (tags, online users, who liked a post) and combine sets with intersections and unions.

Sorted Sets: Leaderboards & Rankings

Keep members ordered by score for leaderboards, top-N lists, priority queues and time-based data.

Counting at Scale: HyperLogLog & Bitmaps

Count millions of unique visitors in 12 KB with HyperLogLog, and track daily activity with bitmaps.

Geospatial: Nearest Drivers & Shops

Store locations and find nearby points within a radius, the core of delivery and ride-hailing apps.

Streams: Reliable Event Logs

Append events with XADD, read them with consumer groups, and acknowledge processing with XACK.

Caching Done Right

The cache-aside pattern, choosing TTLs, invalidating stale data and avoiding cache stampedes.

Sessions & Rate Limiting

Store sessions in Redis so any server can serve any user, and stop abuse with fixed-window and sliding-window limiters.

Job Queues & Pub/Sub

Run background jobs through Redis-backed queues and push real-time messages with publish/subscribe.

Transactions, Lua Scripts & Locks

Make several commands atomic with MULTI/EXEC and Lua, and prevent double processing with distributed locks.

Memory, Expiry & Eviction Policies

Watch memory use, set maxmemory and an eviction policy, and find big keys before they hurt.

Persistence: RDB, AOF & Replication

How Redis saves data to disk with snapshots and append-only files, and how replicas provide high availability.

Securing Redis

Passwords and ACL users, TLS, network binding and disabling dangerous commands.

Redis from Python & Node.js

Use redis-py and node-redis: connections, pipelines, JSON data and error handling.

Redis in Laravel & Django

Use Redis for cache, sessions, queues and rate limiting in Laravel and Django with a few settings.

Project: Flash Sale Backend

Build a flash-sale backend that survives a traffic spike: cached product page, atomic stock, rate limiting, queue and live leaderboard.