Oops, sorry if that wasn't clear, we're not building a search engine index (yet). We'll definitely do it if we get enough people interested in paying for such a product, though. Right now we're using APIs for other search indexes, like Mojeek and Marginalia, then sprinkling some basic local algorithms to tweak the results and apply the preferences to boost/downrank/exclude domains and TLDs (which is everyone's favorite "feature").

Stack-wise, it's very "boring" (as in, it generates and serves the HTML + bits of JS to enhance settings and such), using Deno in the backend and PostgreSQL for the DB.