Senior work owns a block. Principal work owns decisions that several teams live with: which architecture, which risks to carry, what to give up when the plan changes. This topic is one review in two rounds. The first picks an architecture under uncertainty; the second reopens it when four constraints move at once.
2 lessons, about 11 min
The senior answer finds the right architecture. The principal answer also names the one constraint that decides it, puts numbers on the others, separates reversible from irreversible choices, writes down each assumption with an owner, and says what future fact would change the decision.
The whole topic on one page, taken from each lesson's Remember box.
Round 1: Three Architectures, One Decision
Find the one constraint that separates the options; put numbers on everything else.
Under an open question, choose the option that survives its strictest answer, and escalate it with a date.
Anything the decision relies on (a burst cap, a clock) becomes a requirement with an owner.
Rule of thumb: a decision is only as good as the assumptions written next to it.
Round 2: When the Constraints Change
Check each change against the record: confirmed, a named trigger, or new.
A clock change moves bandwidth and latency; recompute both before promising power savings.
Cut reversible or invisible features; protect security and silicon-risk checks.
Rule of thumb: re-decide piece by piece, from the record, not from memory.
Mini project: the capstone: a resilient streaming peripheral, stage by stage
Interview: run a mock interview on this topic