Redis Key Types Explained for Developers and Businesses

Introduction

Redis is a high-performance, in-memory data store used for caching, real-time analytics, messaging, and event-driven systems. Understanding Redis key types and their behavior is essential for building fast, reliable applications.

What Is a Redis Key?

A Redis key is a unique string that maps to a value. The value can be stored using different data structures such as strings, hashes, lists, sets, sorted sets, or streams. Keys can also have expiration times (TTL).

SET user:123:name "Alice"
GET user:123:name

Output:

"Alice"

1. String Keys

Strings store a single value—text, numbers, or serialized data. They are commonly used for caching, counters, and rate limiting.

SET cache:product:1001 "{"id":1001,"name":"LandOfBytes"}" EX  300
GET cache:product:1001
INCR rate_limit:user:42
EXPIRE rate_limit:user:42 60
GET rate_limit:user:42

Explanation: INCR increments a numeric value, while EXPIRE ensures the key automatically expires—an essential rate-limiting pattern.

2. Hash Keys

Hashes store multiple field-value pairs under a single key, making them ideal for representing objects.

HSET user:1001 name "Alice" plan "Pro" status "Active"
HGETALL user:1001

Hashes allow partial updates without overwriting the entire object, saving memory and bandwidth.

3. List Keys

Lists are ordered collections, commonly used for queues and background job processing.

LPUSH queue:email "send_welcome_email:user_123"
LPUSH queue:email "resize_image"
LRANGE queue:email 0 -1

4. Set Keys

Sets store unordered, unique values—perfect for feature flags and membership checks.

SADD feature:beta_users 123 456 123
SMEMBERS feature:beta_users

5. Sorted Set Keys (ZSETs)

Sorted sets store unique elements ordered by score, making them ideal for leaderboards and rankings.

ZADD leaderboard 980 alice
ZADD leaderboard 1200 bob
ZREVRANGE leaderboard 0 1 WITHSCORES

6. Stream Keys

Streams are append-only logs designed for event-driven architectures and real-time pipelines.

XADD orders * order_id 8821 user_id 123 amount 49.99
XREAD COUNT 1 STREAMS orders 0

Key Expiration & TTL

Redis supports automatic expiration of keys, which is essential for sessions, caches, and temporary tokens.

SET session:abc "active" EX 3600
TTL session:abc

Conclusion

Redis key types directly impact performance, scalability, and memory efficiency. Understanding how each structure behaves allows teams to build faster, more reliable systems using Redis.