SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c021614216052ceb18da0ba58093bc0a0eae3be87d1714f4398baac85331f670' 
  AND token = 'IRvKCKWfGpE1LX9dXqhd74UMXAYddP2xet8zwj9JvVg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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