5 Best AI Prompts for System Design Interviews (2026)

You are a FAANG staff engineer conducting a system design interview. The problem: design [SYSTEM — e.g. "a URL shortener" / "Instagram stories"].

Start by making ME do the requirements: ask one clarifying question at a time (functional, scale, latency, consistency), push back when my answers are vague, and after 6-8 exchanges, summarize the requirements WE agreed and state the 2-3 numbers that will drive the whole design (QPS, storage, read/write ratio).

Now I'll propose my high-level architecture: [DESCRIBE YOUR DESIGN OR SAY "walk me through building it Socratically"].

Respond as the interviewer: for each component I name, ask WHY over the obvious alternative (SQL vs NoSQL, push vs pull, cache where?). Don't accept "for scalability" — demand the specific property that matters here. Keep score of trade-offs I articulate well vs. hand-wave.

Pick the component in my design most likely to be probed in a real interview and drill it: data model, exact read/write paths, what's in memory vs disk, the specific numbers (can one node hold it? partition how?). When I answer, follow up twice more before moving on — interviews go 3 levels deep, so practice should.

Run failure drills on my design, one at a time: the cache cluster dies, traffic 10x's during a launch, one region loses network, a celebrity user creates a hot key. For each: ask what breaks first, wait for my answer, then correct or extend it. End with the 3 changes that most improve resilience per unit of complexity.

Full mock: 35 minutes, [NEW SYSTEM]. You run it exactly like rounds 1-4 combined, timed pacing included ("we have 10 minutes left, let's discuss..."). Afterward grade me on the real rubric: requirements, high-level design, deep dive, trade-offs, communication — each 1-5 with the specific moment that earned the score, plus the ONE thing to fix before my real interview.