Welcome. To avoid primary running out of disk space, you can configure max_slot_wal_keep_size https://www.postgresql.org/docs/17/runtime-config-replicatio...

Since Supabase is vanilla Postgres, streambed should work with replica as the source.

reg, Planetscale, I haven't looked at their offerings yet.

Where do you host your DB currently? Happy to try out with that provider as the source.