SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51925d9c5b8004224300026112031a5e24ac1475451aac1bec40a701c9db14f1' 
  AND token = '9krUj1WsL8t2nTdQy7F6BjQe5e7T9m6wfiTlO+SgtpU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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