SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6fa5307504df09ba713710460b19fb2614c8d6b2332453825a68637db8655376' 
  AND token = 'pe42VzgReYs7qazLzKFYiTJnA+5wKfrCmjijWxQVQzA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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