TCP & UDP — Part 4: Interview Q&A

What is this?

This is the part where everything you've learned gets tested under pressure. In an interview, knowing how TCP works isn't enough — you have to explain it crisply, reason about trade-offs out loud, and drop the one line that tells your interviewer "this person has actually debugged this in production."

The one-line idea: transport questions reward people who can hold the tension — reliable on unreliable, flow control vs congestion control, freshness vs correctness — and explain why the trade-off exists, not just that it does.

Let's run them as a mock interview. For each question: what they're really asking, a model answer, and the senior line that lands the point. Keep the running analogy handy — TCP is the careful confirmed phone call; UDP is the shout across the room.