Kidus Tefeta

Two people cannot book the same minute

Checking "is this time free" and then inserting leaves a gap where a second request passes the same check. No amount of application code closes it, so the rule lives in the database: active bookings for one artist may never overlap, and the second one to arrive is refused whatever order they land in.

alter table bh_bookings
  add constraint bh_no_double_booking
  exclude using gist (
    artist_id with =,
    tstzrange(starts_at, ends_at, '[)') with &&
  ) where (status = 'active');

The three functions that write a time catch that refusal and answer with the same sentence a slow-race loser already gets, so the customer sees "that time has just gone" and not an error. sql/084 in the BookHere repository.

The OPE course: your AI coder leaves part of the build for you

People who build with AI end up shipping code they have never read. I am one of them, so I built the fix into my own tool instead of pretending otherwise. Switch a project to Learning while building and OPE writes rules into the project that your AI coder has to follow: it builds as normal, then leaves one or two small pieces of that build for you, at your level, each with a stand-in so the app still runs and a test that fails until your real code is in. It tells you which file and which lines are yours, asks whether you want step by step help, and then builds nothing more on the project until your piece passes its test. Payments, passwords, security and anything that deletes data are never handed to a learner.

1. 0Computer
2. 1Reader
3. 2Tweaker
4. 3Writer
5. 4Builder
6. 5Debugger
7. 6Designer
8. 7Elite

Eight parts, 113 milestones, from a first terminal command to reviewing an AI's code and rejecting it. Every part opens with a door test that passes the whole part if you already know it. A practice bank of 114 tested tasks covers the days your own project has nothing at your level, and it lives in its own folder, never inside your project.

I am working through it on my own projects. That is the honest answer to "you build with AI, so do you understand it": I am closing the gap in public, on a tool anybody can download and check.