Step-by-step articles on Redis, part of our NoSQL & Caching collection.
Showing 10 articles
Redis is an in-memory data store known for sub-millisecond responses. It's more than a key-value cache: each data structure solves a specific class of problems elegantly. Strings: cache values and counters SET page:/pricing "<html>..." EX 300 # cache for 5 min...
A cache in front of a slow database query or API can cut response times from hundreds of milliseconds to one. Getting freshness and failure behaviour right is the hard part. Cache-aside (lazy loading) async function getProduct(id) { const key = `cache:product:...
When several app instances run the same scheduled job, you often want exactly one of them to do the work. A Redis lock is a simple way to coordinate. Acquire with SET NX PX import { randomUUID } from 'node:crypto'; async function acquireLock(name, ttlMs) { con...
Redis Streams are append-only logs with consumer groups. They sit between simple Redis lists and full message brokers like Kafka: persistent, replayable and easy to run. Producing events await redis.xAdd('orders', '*', { // '*' = auto-generated id (timestamp-s...
Pub/Sub lets one process publish a message to a channel and every subscribed process receive it instantly. A classic use is keeping WebSocket servers in sync. The problem it solves With three app instances behind a load balancer, user A's WebSocket might be on...
Ranking millions of players by score with SQL means sorting large tables. A Redis sorted set keeps members ordered by score at all times, so rank queries take microseconds. Adding and updating scores await redis.zAdd('lb:global', [{ score: 1520, value: 'asha'...
For years Redis was BSD-licensed open source. In 2024 Redis (the company) switched new versions to source-available licences. In response, contributors forked the last BSD version as Valkey , hosted by the Linux Foundation. Later, Redis added the open-source A...
Redis keeps data in memory. Whether anything survives a restart depends on its persistence settings, and the right choice depends on how you use Redis. RDB: point-in-time snapshots # redis.conf save 3600 1 # snapshot if at least 1 change in an hour save 300 10...
The default in-memory session store loses every session on restart and doesn't work with more than one server. Redis is the standard fix: fast, shared and with built-in expiry. Setup npm install express-session connect-redis redis import express from 'express'...
Redis lives in RAM, so memory is the resource you'll manage most. Without limits, a growing cache can exhaust the server and get Redis killed. Set a limit # redis.conf maxmemory 2gb maxmemory-policy allkeys-lru Leave headroom on the machine for the OS, client...
