SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dc51ad4f3903c29522b62bab7a5509c76dd4d9ae089d30e11f43b67663145890' 
  AND token = 'CQF46li87sgB9I+GnCIYhDQP7hvYYlFZEKUD1DtCjUI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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