There is a misconception about what separates senior engineering work from staff-level work: that the next step is simply more code, harder algorithms or deeper knowledge of framework internals.
As I began targeting Staff and Principal-level roles, I paid more attention to a different kind of conversation. Can I explain not only how to build a thing, but whether it is the right thing to build under these constraints?
Ambiguity as a Test
Technical ambiguity does not arrive neatly separated from organisational ambiguity. A design can be sound in isolation and still create problems for the people and systems around it.
A useful question to prepare for is: if this interface changes, who depends on its current behaviour, and how will the transition work? That is an illustrative question, not a quotation from an interview panel. It asks about contracts, coordination and the consequences of a decision.
The point is not that senior engineers ignore those concerns. It is that a broader role makes explaining and resolving them a larger part of the job.
System Design Beyond the Diagram
Naming Redis or Kafka is a beginning. A more complete discussion includes why the system needs them, what operating them will involve and which simpler option was considered.
I think of this as constraint mapping. The design has a happy path, failure states, delivery limits and people who will maintain it. Communicating those together is more useful than presenting an impressive collection of boxes.
Interview formats vary. My preparation is to practise making a decision understandable: state the problem, name the trade-off, explain what would change my mind and connect the implementation to the outcome.
That is a different skill from solving a coding exercise, and it deserves deliberate practice too.