Osvitly

What was technically hard

Assessment under load. Everyone submits in the last hour before a deadline, so the write path has to stay correct while the read path is being hammered, and a partial submission can never be lost.

How it's built

Django and DRF, PostgreSQL, Redis for the queue, React on the front end.

One decision we made, and why

We chose to write submissions to durable storage before acknowledging them, accepting slightly slower acknowledgement in exchange for never losing a student's work. On a deadline night that trade is not close.