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.
On MySQL 8, a new user "Jose" gets "username already taken". The only other user is "José", and the stored bytes are different. You remove the app's own duplicate check, and the UNIQUE index still rejects the insert.
Why does the database think Jose and José are equal?
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.