I can check that
views-exposure-filter.tpl.php is loading for basic JSON endpoints that do not return any form fields: My autocomplete – / search_api_autocomplete / search_api_views_flc_biz_search / – / farm – is driven by the view below against Solr, and I use the project / ajax_facets for POST.
/ ajax / ajax_facets / refresh to filter by other indexed fields.
This stop point confirms that I always load unnecessary templates when calling json APIs. I have not yet plunged into the stack trace or scattered more stopping points to find out what is really charging this, but be aware that it might take several hours before you can perform a thorough analysis.
To dramatically improve performance, how can I avoid the entire D7 theme layer when requesting JSON?