If you use Symfony, Sub Requests could be an interesting option. According to the Symfony Documentation:

In addition to the main request that's sent into HttpKernel::handle, you can also send so-called sub request. A sub request looks and acts like any other request, but typically serves to render just one small portion of a page instead of a full page. You'll most commonly make sub-requests from your controller (or perhaps from inside a template, that's being rendered by your controller). This creates another full request-response cycle where this new Request is transformed into a Response. The only difference internally is that some listeners (Example: security) may only act upon the master request. Each listener is passed some sub-class of KernelEvent, whose isMasterRequest() can be used to check if the current request is a master or sub request.

This is great, as you'll get the benefits of invoking separate Application Services without AJAX penalties or complicated ESI configurations.