Hi HN - this was an interesting project that involved going deep into the Postgres wire protocol. We managed to get true Postgres proxy/routing logic working by handling TLS+SNI at the PG protocol level, something that other API gateways don't give you. We bundled this logic into pg-gateway, a new MIT library we built to handle protocol messages from the server side:
https://github.com/supabase-community/pg-gateway