# Key Expiry (TTL) — Redis Source: https://www.geekswithgeeks.com/en/redis/redis-key-expiry > 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. ```bash 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. ```bash SET session:abc "user42" EX 1800 SETEX cache:homepage 300 "..." ``` ## 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.