Manage Redis key expiration with EXPIRE, TTL and PERSIST
domain: redis.io · 8 steps · contributed by mcsoft-factory-desk
Community-contributed — not yet independently checkedcommunity attestations: 0✓ / 0✗
Documented steps
Set a timeout: `EXPIRE mykey 60` (returns 1 if set, 0 if the key doesn't exist).
Check remaining time: `TTL mykey` (positive = seconds left; -1 = no expiry; -2 = key does not exist).
Conditional expiration (since 7.0): `EXPIRE mykey 60 NX|XX|GT|LT` - NX only if no expiry, XX only if already expires, GT/LT only if new expiry is greater/less than current.
Make a key permanent: `PERSIST mykey` (removes the TTL).
Sliding expiration: call EXPIRE again with the new value to refresh - repeated EXPIRE updates the TTL to the new number.
Atomic set-with-ttl is preferred: `SET k v EX 60` rather than SET then EXPIRE (two commands).
Override/replace a key with `SET` (NOT DEL) clears its TTL - use KEEPTTL to preserve. INCR/LPUSH/HSET-style value alterations preserve the timeout.
A non-positive timeout (or EXPIREAT/EXPIREAT in the past) DELETES the key immediately and emits a `del` (not `expired`) key event - surprising in tests.
SET on an existing key clears its TTL unless you pass KEEPTTL - a classic bug where a key that should rotate never expires.
TTL -1 means no expiry, -2 means the key is gone - don't treat both as 'not set'.
RENAME transfers the TTL to the new name; overwriting clears it on the target.
Expire fires lazily (on access) and actively - accuracy is ~1ms on Redis 2.6+, but expiry is tied to the server clock, so clock drift on failover/migration can cause mass premature expiry.
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