How to Set Cache Expiration in Redis: Simple Guide

In Redis, you set cache expiration using the EXPIRE command to specify a time-to-live (TTL) in seconds for a key. Alternatively, you can use the SET command with the EX option to set a key with an expiration time in one step.

Syntax

The EXPIRE command sets a timeout on a key in seconds, after which the key is deleted automatically. The SET command can also set a key with expiration using the EX option for seconds or PX for milliseconds.

• EXPIRE key seconds: Set expiration time in seconds.
• SET key value EX seconds: Set key with value and expiration in seconds.

redis

EXPIRE mykey 60
SET mykey "value" EX 60

Example

This example shows how to set a key with a value and expire it after 10 seconds using both EXPIRE and SET commands.

redis

SET session_token "abc123"
EXPIRE session_token 10
TTL session_token

SET cache_item "data" EX 10
TTL cache_item

Output

OK
1
10
OK
10

Common Pitfalls

One common mistake is forgetting to set expiration, which causes keys to persist indefinitely and can fill up memory. Another is setting expiration on a key that does not exist, which returns 0 and does nothing. Also, using SET without expiration when you want a temporary cache is a frequent error.

redis

EXPIRE missing_key 30  # returns 0 because key does not exist

# Correct way:
SET temp_key "value" EX 30  # sets key with expiration in one step

Quick Reference

Command	Description	Example
EXPIRE key seconds	Set expiration time in seconds	EXPIRE mykey 60
SET key value EX seconds	Set key with value and expiration	SET mykey "val" EX 60
TTL key	Check remaining time to live	TTL mykey

Key Takeaways

Use EXPIRE to add expiration to existing keys in seconds.

Use SET with EX option to set key and expiration in one command.

Check TTL to see how much time is left before a key expires.

Remember keys without expiration persist and can fill memory.

Setting expiration on non-existing keys does nothing.