SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '257f45eb7d799b8f1100a55768dd2c679702b37c8d52e59f9046e849fbb76533' 
  AND token = 'yZso+Dcq3ZzYHOVNJujB/x81xRGg7MA6YMZJN8Nmc2k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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