SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '388799eb075d0c15a5bab59363a05896a4c2c919be0fe92e387d15c5df257555' 
  AND token = '1aDToZc6vqdrLpdB3hlAbkxyn+dvvEimGu65/eFDHMM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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