SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '19df34e1bd423ee256111ce4bbd4c995fbf3d018736b0b4105aa447ae6f99787' 
  AND token = '/KAGUnN671Mz5TWnP6ex6QATZ5aQd3RZItslwICjT+U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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