Taking some inspiration from this thread, I made a template repo for Netlify functions so that one can deploy an inbox easily (everything else can technically be hosted statically). A reference implementation for Firestore is in my personal fork (running on @admin@musakui-ap.netlify.app )
I don’t know if I’m handling everything in the AP and http signatures spec correctly, everything so far is through actually following people and fixing errors in the logs (e.g. https://hellsite.site requires a signed GET for retrieving signatures).
The overall idea with this is to handle everyhing that isn’t the inbox on your own computer. Have a local server that handles your activities (e.g. liking posts), and if you make any posts or follow anyone just generate the appropriate application/activity+json files and update a static site.
I hope to break out some of the utilities into a library, but just wanted to keep everything self-contained for this serverless thing for now.