I have similar. One PG database per tenant (640). Getting the current DSN is part of auth process (central auth DB), connect through PGBouncer. Schema migratio

I have similar. One PG database per tenant (640). Getting the current DSN is part of auth process (central auth DB), connect through PGBouncer. Schema migrations are kind of a pain, we roll out changes, so on auth there is this blue/green decision. Custom fields in EAV data-tables or jsonb data. Backups are great, small(er) and easier to work with/restore. Easier to move client data between PG nodes. Each DB is faster than one large one. EG: inventory table is only your 1M records, not everyone's 600M records so even sequential scan queries are pretty fast.