Practice
Mock Interviews
Timed, staged, and scored against a rubric you only see afterwards — the same order a real round happens in. 8 problems, weighted toward the ones the chapter decks don't already cover.
How to use these
Talk out loud, and write as if someone is watching — the scratchpad is your whiteboard. Do not read the model answer first; the entire value is in producing the structure yourself under a clock. Score honestly, then re-run the same problem a week later.
Warm-up
Core
Design a ride-hailing service
geospatial · matching · real-time · state-machine
45 min
Design a payment ledger
transactions · idempotency · correctness · audit
45 min
Design a metrics and alerting system
time-series · ingestion · aggregation · storage
45 min
Design a feature flag service
configuration · caching · consistency · low-latency
45 min