Supabase Auth uses GoTrue, which is a Go server. It's all open-source, so you can self host it as much as you want.
You can see how it fits into the full Supabase Architecture here: https://supabase.com/docs/guides/getting-started/architectur...
You can see how it fits into the full Supabase Architecture here: https://supabase.com/docs/guides/getting-started/architectur...