If you're using Postgres then using the ltree module is great for permission systems. Available in RDS too

>We added a point of failure, as the permissions table can get out of sync with the actual data.

>The main risk with pre-computed permissions is data getting out of sync.

It would make sense to have permissions be a first class concept for databases and to ensure such a desync could never happen. Data being only read or written from specific users is a very common thing for data so it would be worth having first class support for it.