Implementing a KV Store on top of MySQL

Implementing put, get, del, ttl operations all in sync. To implement this in space efficient way, following is our table structure :

+------------+--------------+
| Field      | Type         |
+------------+--------------+
| key        | varchar(255) |
| value      | text         |
| expired_at | datetime     |
+------------+--------------+

Running put operation

Put Query:

REPLACE INTO kv_store VALUES (?,?,?)

Running get, del, ttl operations

Get Query:

SELECT value FROM kv_store WHERE `key` = ? AND expired_at > NOW()

Del Query:

UPDATE kv_store SET expired_at = '1970-01-01' WHERE `key` = ? AND expired_at > NOW()

TTL expiry Query:

DELETE FROM kv_store WHERE expired_at <= NOW() LIMIT 1000

KV store after the automatic go routine to delete expired keys

We run a go-routine ttlCleanupRoutine that cleans expired keys after every 2 minutes.