I just did a full write up on the Architecture becaase we have this question often: https://supabase.com/docs/architecture#architecture

> most of their current stack and active development, frontend and backend, is Next.js

This is only the Dashboard. We dogfood Supabase to build Supabase, so we use the tools in the doc above

No better clarification than the author! In my mind, I was thinking of just the web framework UI-for-CRUD comparison, where Next.js is supplanting what Rails is typically used for (like your Dashboard / GUI, and most of the core webapps for the previous 2010 Rails co's), but fair enough, you're probably leveraging a lot more of your own PostgREST, triggers, functions, & webhooks than a typical backend Next shop.