Problems / Design a product, medium
Design Shopify from an empty canvas: thousands of merchants’ storefronts and product pages served fast, checkout for all of them, and one store’s flash sale kept from hurting the rest.
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Request types to route: storefront (75%, read), product (22%, read), checkout (3%, write). Budget: $115,000 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 ≤ 200 ms (storefront); p99 latency ≤ 300 ms (product); p99 latency ≤ 3.0 s (checkout) |
| A flash sale on one store | At 5 s a celebrity drop starts on one store: traffic jumps to 4× for 8 s. | Success ≥ 99%; p99 latency ≤ 400 ms (product); p99 latency ≤ 4.0 s (checkout) |
| 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 (storefront) |
| DDoS attack | At 5 s 20,000 requests a second of flood traffic arrive for 10 s, alongside real users. | Attack blocked ≥ 95%; Success ≥ 99% |
| A server dies | At 4 s one server of the first app service on the request path dies for 10 s. | Success ≥ 99% |
| Budget: $115,000/month | The normal day's design must cost at most $115,000 a month. | Cost ≤ $115,000/month |