Tune postgres

- [ ] [postgres mvcc garbage](https://www.cs.cmu.edu/~pavlo/blog/2023/04/the-part-of-postgresql-we-hate-the-most.html)
- [ ] [Nine ways to shoot yourself in the foot with PostgreSQL](https://philbooth.me/blog/nine-ways-to-shoot-yourself-in-the-foot-with-postgresql)

Start by reading the linked articles on PostgreSQL MVCC garbage and common PostgreSQL pitfalls, then inspect how this repository uses PostgreSQL. No files, tests, or concrete tuning target are named; the work is done only after the relevant database improvements are identified, implemented, and verified.

Written by the indexing model from the issue text.