SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd6538921283c621f04c26ce1814f75026edd85032c6d88c765d5dab1e94359fc' 
  AND token = 'Kh+BwbW/7QYzL/uOpZDwpfuv1xXYLnASp+PqNCxRSl4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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