Problems / Design a product, hard
Design Netflix from an empty canvas: a personalised home page, play starts with DRM, video segments from a CDN and progress heartbeats, at 2,500 requests a second.
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Request types to route: browse (34%, read), play (2%, read), segment (48%, read), heartbeat (16%, write). Budget: $14,000 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 ≥ 99.5%; p99 latency ≤ 400 ms (browse); p99 latency ≤ 800 ms (play); p99 latency ≤ 300 ms (segment); Success ≥ 99.9% (heartbeat) |
| Friday night | At 5 s the evening peak arrives: traffic doubles for 8 s. | Success ≥ 99%; p99 latency ≤ 600 ms (browse); p99 latency ≤ 1.2 s (play) |
| The title metadata cache flushed | At 5 s the title metadata cache is emptied, as after a restart or a bad deploy: every read misses until it warms up again. | Success ≥ 99%; p99 latency ≤ 800 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: $14,000/month | The normal day's design must cost at most $14,000 a month. | Cost ≤ $14,000/month |