SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '644db7452ee752470f44d121f3225db5058ad271b3828572928516d9d90e0421' 
  AND token = 'xv1/TVawXOtG3YzMWLEBYNc4MskJbKIqcnvhsevPhDo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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