SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3a6b760778e7309fd7b975215b7ba8fb42e94901e6e32bb9d0b7d22045aec7f8' 
  AND token = '4pZZYrj6bLKfkkwGaJB29jkGvRSgUzniDT7KCdvdhCg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}