Problems / Design a product, medium
Design LinkedIn’s connections from an empty canvas: cached profiles, a connection graph, precomputed “people you may know”, and messaging.
Unlock it once for 15 credits; everything inside it is free (runs, changes, Submit, results, hints). Sign in with Google to start; new accounts get free credits.
Request types to route: profile (50%, read), message (25%, write), pymk (15%, read), connect (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 ≤ 200 ms (profile); p99 latency ≤ 200 ms (pymk) |
| Monday job hunt | At 5 s Monday morning arrives: traffic doubles for 8 s. | Success ≥ 99%; p99 latency ≤ 400 ms (profile) |
| Cache flushed | At 5 s the cache on the request path is emptied, as after a restart or a bad deploy. | Success ≥ 99% |
| Database 3× slower | At 5 s the main database on the request path answers 3× slower for 8 s. | Success ≥ 99% |
| Budget: $7,500/month | The normal day's design must cost at most $7,500 a month. | Cost ≤ $7,500/month |