Examination at Scale: Queues, Databases, and ACKs
When Sara is taking her exam, the last thing she has on her mind is whether clicking “submit” will actually work. The exam ends: in the last two minutes of the window, most of the class hits submit at the same time. It’s not only the class — these are central exams, everyone in the country is submitting at the same time. When the system shows “Submitted”, this is a promise to Sara that her exam is now safely stored with it and she doesn’t need to worry. ...