UPI Platform (Walnut Switch: Routing, Deemed Payments, Net Settlement for 741 Banks)
Design the UPI switch like NPCI's: routing between 741 banks, both legs in 15 seconds, deemed approvals, reversals and net settlement 10 times a day.
The Engineering Career Operating System
More than interview prep. Your path forks at Senior, into building (IC) or leading (management). Pick a goal, see the real bar, and follow the exact path to get there.
Built by Staff Engineers, Principal Engineers, and Engineering Leaders who've built systems, led teams, and hired engineers.
The bar for each level is the real one, not generic advice.
Your app's own scheduler starts the billing report when the Berlin clock reads 02:30. It ran twice on 27 October 2024, and never on 30 March 2025. Only one app instance runs, and its clock is synced.
Why did the job run twice, then not at all?
Pick one. If it is wrong, you will see why, and you can try again.
Pick a level and be honest. Could you actually answer each of these out loud, right now? If several are shaky, that is the gap, and that is exactly what the path is for.
The bar: Design across services, make and defend trade-offs, and lead a design review.
If several are shaky, you are probably not there yet. Here is the path.
See the Senior Engineer pathWhether you are building LLM systems or getting grilled on them, go deep: the foundations, the engineering, the security, and the AI system design round. Read a full lesson free before you decide.
Now we also crack a few walnuts out loud, on video. Everything here stays right where it is.