Full mock · 45 minutes · August 18, 2025 · This is an example of the report every session generates.
Solid backend fundamentals and clear communication. System design depth is the fastest lever for your next session.
Q1Tell me about the most complex system you've designed.
8.0 / 10“I led the rebuild of our checkout service, splitting a Django monolith into three services with a Postgres-backed order store and Redis for idempotency keys. Peak load was around 400 orders per minute during sales events.”
Coach note: Concrete scope, real numbers, clear ownership. To push higher, name one hard trade-off you made and why.
Q2How would you scale that checkout system to 10x traffic?
6.0 / 10“I would add more servers and caching, and maybe use a message queue so nothing gets lost. We could also shard the database if it gets slow.”
Coach note: Directionally right but generic — no bottleneck analysis, no cache-invalidation or queue-backpressure detail, nothing on metrics or alerting. This is the gap to close next.
Q3Tell me about a disagreement you had with a teammate.
8.5 / 10“Our frontend lead wanted client-side polling for order status; I argued for websockets with a polling fallback. We prototyped both over two days, measured battery and server cost, and shipped the hybrid. No hard feelings — the data decided.”
Coach note: Excellent STAR structure: situation, your position, how you resolved it, and the outcome. Clear and concise.