What main data types does Redis support?

RedisJunior~2 min read

Redis supports a set of core data structures, each implemented as efficiently as possible for storage and manipulation in RAM. These types are the foundation of everything Redis does.

1. String

The simplest, most basic data type, key-value. It can store text, numbers, JSON, binary data, images, and more.

Example:

bash

SET user:name "Alice"
GET user:name

Arithmetic is supported:

bash

INCR counter
DECRBY counter 5

A quirk: a string in Redis can be up to 512 MB.

2. List

An ordered collection of strings, like a queue or a stack. Elements can be added and removed from either end.

Example:

bash

LPUSH queue task1
RPUSH queue task2
LPOP queue

Uses: task queues, event feeds, chats.

3. Set

An unordered set of unique elements. Supports set-theory operations: intersection, union, difference.

Example:

bash

SADD tags "redis" "database" "cache"
SMEMBERS tags
SISMEMBER tags "redis"

Uses: storing unique IDs, subscribers, tags.

4. Sorted Set

Like Set, but every element has a score, a number that determines the sort order.

Example:

bash

ZADD leaderboard 1500 "Alice" 1700 "Bob"
ZRANGE leaderboard 0 -1 WITHSCORES

Uses: rankings, leaderboards, prioritization, top lists.

5. Hash

Holds a set of field-value pairs under a single key. It resembles a mini-object or JSON.

Example:

bash

HSET user:100 name "Alice" age 25
HGET user:100 name
HGETALL user:100

Uses: user profiles, configuration, metadata.

6. Bitmap

Lets you store and manipulate individual bits of a string.

Example:

bash

SETBIT users_online 100 1
GETBIT users_online 100
BITCOUNT users_online

Uses: activity tracking, online statistics, boolean flags.

7. HyperLogLog

A structure for the approximate counting of unique elements with minimal memory use (~12 KB).

Example:

bash

PFADD visitors "user1" "user2" "user3"
PFCOUNT visitors

Uses: counting unique users, IPs, events.

8. Stream

A log of structured events (like Kafka). Supports message IDs, consumer groups, acknowledgments.

Example:

bash

XADD events * user "Alice" action "login"
XREADGROUP GROUP g1 c1 COUNT 1 STREAMS events >

Uses: task queues, events, microservices, logging.

9. Geo (geospatial data)

Lets you store coordinates and run geo-queries (finding nearby points, distances).

Example:

bash

GEOADD shops 30.5 50.4 "ShopA"
GEORADIUS shops 30.5 50.4 10 km

Uses: maps, logistics, tracking, "near me" search.

Summary

Type	Purpose	Example use
String	Strings, numbers, JSON	Cache, tokens, counters
List	Ordered collections	Queues, feeds
Set	Unique elements	Subscriptions, tags
Sorted Set	Prioritized elements	Rankings, leaderboards
Hash	Objects, dictionaries	Profiles, configs
Bitmap	Bit-level flags	Online activity
HyperLogLog	Counting unique items	Analytics
Stream	Event streams	Queues, logging
Geo	Geo-coordinates	Distance search

Redis isn't just a key-value store, it's a set of highly efficient in-memory data structures that can be combined for any scenario, from caching to streaming analytics.

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