Hi,
Thank you for the details!
To achieve the exact same grouping I have changed the configuration to a content type grouping, like so: https://i.imgur.com/OsUwarN.png
To maximize the performance I have enabled the index table engine. After that I did some testing on the responsiveness, and the search process now finishes within ~0.06 seconds accoring to the measurments, which is exceptionally good (meaning the optimization works).
I have also tested the server XHR response time, which is ~1.4 seconds for a completely empty request, meaning that is the minimum overhead added on top of Ajax Search Pro response times – so the total average response time is therefore 0.06 + 1.4 seconds. There is always some overhead, as this is the general time for WordPress to run initialize. This can be further improved by turning off unused plugins, removing unused code snippets etc..
I usually aim to use as few plugins as possible (mostly less than 10), but of course plugin quality also matters. The 1.4s overhead seems about average to me. On very highly optimized servers it’s around 0.4 seconds or even less, but that requires a lot of code optimization.
Chances are that on production it’s going to be lot less, as staging environments are usually shared on resources so they are not as quick as the production counterparts.