Lesson 5 / 18

Key Expiry (TTL)

Make keys disappear automatically — the backbone of caching.

EXPIRE & TTL

EXPIRE sets a countdown in seconds after which the key is deleted; TTL checks how much time is left.

SET otp:9876 "4521"
EXPIRE otp:9876 60
TTL otp:9876

Output:

OK
(integer) 1
(integer) 58

Expiry in one line

SET key value EX seconds sets the value and TTL together — no separate EXPIRE call needed.

SET session:abc "user42" EX 1800
SETEX cache:homepage 300 "<html>...</html>"

Why expiry matters

TTLs let Redis act as a self-cleaning cache — stale data times out on its own instead of piling up in memory forever.