How to Use TTL in Redis: Set Expiry for Keys Easily

In Redis, you use the EXPIRE command to set a TTL (time to live) on a key, which makes the key automatically delete after the specified seconds. You can check the remaining TTL with TTL and remove the expiration with PERSIST.

Syntax

The main commands to work with TTL in Redis are:

• EXPIRE key seconds: Sets the expiration time in seconds for the given key.
• TTL key: Returns the remaining time to live of a key in seconds.
• PERSIST key: Removes the expiration from the key, making it permanent.

redis

EXPIRE mykey 60
TTL mykey
PERSIST mykey

Example

This example shows how to set a key with a TTL, check its remaining time, and then remove the TTL to keep the key forever.

redis

SET mykey "Hello"
EXPIRE mykey 10
TTL mykey
PERSIST mykey
TTL mykey

Output

OK
1
10
1
-1

Common Pitfalls

Common mistakes when using TTL in Redis include:

• Setting TTL on keys that do not exist, which returns 0 and does nothing.
• Expecting TTL to work with commands that overwrite keys without resetting TTL.
• Confusing TTL output: -1 means no expiration, -2 means key does not exist.

redis

EXPIRE nonexistentkey 10
# returns 0 because key does not exist

SET mykey "Hello"
EXPIRE mykey 10
SET mykey "World"
TTL mykey
# TTL may be reset or lost depending on command used

Output

0
OK
1
-2

Quick Reference

Command	Description
EXPIRE key seconds	Set expiration time in seconds on a key
TTL key	Get remaining time to live of a key in seconds
PERSIST key	Remove expiration from a key
SET key value EX seconds	Set key with value and expiration in one command
DEL key	Delete a key immediately

Key Takeaways

Use EXPIRE to set a TTL in seconds on a Redis key to auto-delete it after time.

Check remaining TTL with TTL; -1 means no expiration, -2 means key missing.

Use PERSIST to remove TTL and keep the key permanently.

Setting TTL on a non-existing key does nothing and returns 0.

Some commands may reset or remove TTL when overwriting keys.