Part 4 — RPC in System Design & Interview Q&A

(maang.io System Design Series)

What is this?

The first three parts built your mental model: RPC is a local-looking call over a leaky network (Part 1), wrapped in serialization, transport, discovery, balancing, and resilience machinery (Part 2), governed by delivery semantics you make safe with idempotency (Part 3). This part is the performance — a mock interview where you turn that model into the crisp, senior answers an interviewer is actually listening for.

The pattern for each question is the one good mentors use: first what they're really asking (the hidden intent behind the words), then a model answer (how to walk through it out loud), then the senior line — the single sentence that signals you've operated this stuff at scale, not just read about it.

The one-line idea: at the Staff/Principal level, nobody is impressed that you can use RPC — they're listening for whether you respect what it hides: the leaky network, the partial failures, the delivery semantics, and the blast radius when a dependency dies.