Ask HN: How would you build Stripe Sigma

Stripe provides https://stripe.com/sigma which allows users to write their own SQL.

If you had a multi-tenant Postgres DB, how would you build a system such as Stripe Sigma? Where each tenant can only query their own data obviously.

Thanks for any recommendations!

More notes that could be helpful:

* dozens of tables

* data latency should be minimized, but 5 minutes is fine.

* not "big data", <10 GB per tenant

* need a post-processing step (for example, add a column of current balance to each transaction in an accounting system)