Keys & Strings: Overview

🎁 Run Redis in Docker first

Start a local Redis, then open its CLI:

docker run -d --name redis -p 6379:6379 redis:7-alpine
docker exec -it redis redis-cli

Leave this CLI open and paste each lesson's commands into it. (No Docker? Install Redis locally.)

What is a Redis key?

Redis is a key–value server. Every piece of data you store — a counter, a cached page, a session token — lives under a key. Keys are binary-safe strings up to 512 MB, though in practice you should keep them short and meaningful.

A Redis value always belongs to one of the built-in types: String, List, Hash, Set, Sorted Set, Stream, and more. The String type is the simplest: a key maps directly to a single value, which can be text, a number, or raw binary.

127.0.0.1:6379> SET user:1 "Ada"
OK
127.0.0.1:6379> GET user:1
"Ada"

What this module covers

Lesson	Topic
Keys & Strings: Overview	This page — types, keys, and your first SET/GET
SET & GET	All SET options, MSET/MGET, APPEND, STRLEN
Expiration & TTL	EXPIRE, TTL, PERSIST, lazy vs active expiry
Counters	INCR/DECR, atomic increments, rate counters
SCAN & Key Ops	EXISTS, DEL, TYPE, RENAME, KEYS vs SCAN

Your first SET and GET

Let’s store and retrieve a value. Paste these commands into the redis-cli you opened above:

127.0.0.1:6379> SET greeting "Hello, Redis!"
OK
127.0.0.1:6379> GET greeting
"Hello, Redis!"

SET greeting "Hello, Redis!"
GET greeting