Design number 3: Two million games, one running clock
Plate two: two players sharing one truth while the clock runs, and why the bravest thing a real-time system can do is stop.
The blueprint room
Full system designs, drawn carefully and then set on fire. The baseline at a brisk walk, the failure modes at length, and the question every entry keeps asking: which half of this is allowed to die, and did anyone choose that?
Design number 2: A payment system that refuses to guess
The second in the series: a system where the dangerous failure is not downtime but doubt, and where the guardrails exist to stop the machine resolving that doubt with optimism.
Design number 1: Designing a URL shortener for its worst day
Resilience is a design input, not a deep dive at the end. The first in a series: the smallest system everyone knows, designed around the question of what is allowed to die.