Problems / Design a product, medium
Design a food delivery app from an empty canvas: browse restaurants, order and pay, dispatch a rider, and track the order live, through the dinner rush.
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Request types to route: browse (55%, read), track (25%, read), ping (17%, write), order (3%, write). Budget: $68,000 a month.
You start from an empty canvas. When you run the tests, each one simulates your design with its own traffic and failures:
| Test | What it does | Passes when |
|---|---|---|
| Normal day | The normal day: the traffic in the brief, nothing broken. | Success ≥ 99%; p99 latency ≤ 300 ms (browse); p99 latency ≤ 200 ms (track); p99 latency ≤ 3.0 s (order) |
| The dinner rush | At 5 s the dinner rush starts: traffic jumps to 3× for 8 s. | Success ≥ 99%; p99 latency ≤ 500 ms (browse); p99 latency ≤ 400 ms (track) |
| Cache flushed | At 5 s the cache on the request path is emptied, as after a restart or a bad deploy. | Success ≥ 99%; p99 latency ≤ 600 ms (browse) |
| A server dies | At 4 s one server of the first app service on the request path dies for 10 s. | Success ≥ 99% |
| Budget: $68,000/month | The normal day's design must cost at most $68,000 a month. | Cost ≤ $68,000/month |