Design a task management system with tasks broken into sub-tasks.

"I was pulled in directly by a recruiter, and the loop was iterative: each round only unlocked if I passed the previous one. The interviews themselves were pretty simple on the surface, but they were wide and very practical: a small coding problem, then straight into real questions about abuse prevention, UX, latency, and monetization. The messy part was the operations side. Schedules kept moving, and company policy changed. I ended up doing extra late-night calls and two hiring manager conversations because the manager changed in the middle. Even with that chaos, it was one of the most efficient big-company processes I've had, and I ended up signing the offer after a very direct comp conversation."