Problems / Design a product, medium
Design Google Photos from an empty canvas: upload photos, make thumbnails in the background, browse and search the library, at 2,000 requests a second.
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Request types to route: browse (45%, read), thumb (35%, read), upload (12%, write), search (8%, read). Budget: $10,500 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 (browse); p99 latency ≤ 300 ms (thumb); Success ≥ 99.9% (upload) |
| New Year’s Eve | At 5 s midnight strikes somewhere big: traffic triples for 8 s, uploads included. | Success ≥ 99%; p99 latency ≤ 500 ms (browse); Success ≥ 99% (upload) |
| 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 ≤ 500 ms (thumb) |
| A server dies | At 4 s one server of the first app service on the request path dies for 10 s. | Success ≥ 99% |
| Budget: $10,500/month | The normal day's design must cost at most $10,500 a month. | Cost ≤ $10,500/month |