Problems / Design a product, medium
Design Spotify from an empty canvas: stream audio through a CDN, search the catalog, open playlists and log every play, at 2,000 requests a second.
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Request types to route: stream (50%, read), playlist (25%, read), search (15%, read), play (10%, write). Budget: $7,500 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 ≥ 99.9%; p99 latency ≤ 300 ms (stream); p99 latency ≤ 200 ms (playlist); p99 latency ≤ 400 ms (search) |
| A big album drops | At 5 s a superstar releases an album: traffic triples for 8 s. | Success ≥ 99%; p99 latency ≤ 400 ms (stream); p99 latency ≤ 400 ms (playlist) |
| The playlist cache flushed | At 5 s the playlist cache is emptied, as after a restart or a bad deploy: every read misses until it warms up again. | Success ≥ 99%; p99 latency ≤ 500 ms (playlist) |
| A server dies | At 4 s one server of the first app service on the request path dies for 10 s. | Success ≥ 99% |
| Budget: $7,500/month | The normal day's design must cost at most $7,500 a month. | Cost ≤ $7,500/month |