How to correctly implement an AJAX framework on MODX Revo?

Question

MODX

Prompt in terms of the correct structure and optimization of queries to the database.
For statics, everything is clear - from the main page there is a request for the engine.php file, it makes a request to the database, processes the result and returns back to the main page, and that page displays everything beautifully.
In MODX? From the main send the request to a static file (where is it safe to put it?) or to a page that contains a snippet that handles the request?
Almost the entire site is planned for AJAX, no more than 5 pages.

Answer 1

Create a resource with an empty template, put a non-cached snippet there and access this resource.