First of all I'm very sorry if this question does belong, if so please let me know where I should post it if possible.
I have recently discovered ESI and Hinclude as ways to boost my side performance, but I have searched up and down and could not find any document on how search engines will index the pages using these. I would think that since hinclude use javascript it would not be possible for search engines to index the content included dynamically by them. I'm not so sure about ESI, does the content get indexed or will it be left out as well? I hope someone can shed some light on me on this topic.
Regards
ESI is processed "edge-side" - for example Akamai or Varnish. So the client never sees the ESI include tags, they see the fully rendered page.
HInclude processes client-side which means the search engine's spider will need to be able to process JavaScript. Search engines seem to be moving this direction but they may not all support it.