Looking at the repo's mix file it seems to use poolboy for pooling. Given that dashbit and José helped out, was nimble_pool considered?
We made sure to do local benchmarks along the way and there wasn't a meaningful difference.
Really the discussion was around doing as little message passing as possible to not copy data.
See:
https://github.com/supabase/supavisor/pull/4
https://github.com/supabase/supavisor/issues/7
So there are definite gains there but if we want to do things across a cluster we're going to be copying data. The decision at the time was the benefits of clustering outweighed the perf gains considering we were basically already as fast as PgBouncer. This could change.