> On 2, I mean these (feeds, topic lists etc.) are probably not worth indexing at all, esp. since you keep all old content in the index.

Yeah indeed. A better implementation for now would be to let people save single posts, or sync with likes, shares, tweets and retweets, so people can search with those facettes.

> Is your code all home-built, or you're using some FT engine compiled to Wasm?

For the search we are using dexie.js, the rest is home-built. Our storage engine is: https://github.com/worldbrain/storex