SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd21cf6d339c3965fdb5082137f8a04811a3daf44bd3002697b8d4bb09b43834f' 
  AND token = 'mfMKyXLsx9MOhM+G/sVfoYto0YAi2euordNjme64V4o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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