Problems / Design a product, hard
Design a Datadog-style monitoring system from an empty canvas: agents push metric batches into an intake, a stream feeds a time-series database, dashboards query it, and alerts page someone.
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Request types to route: ingest (88%, write), query (12%, read). Budget: $3,800 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 ≤ 30 ms (ingest); p99 latency ≤ 100 ms (query) |
| An incident | At 5 s an incident starts: hosts flood metrics and everyone opens dashboards, 3× traffic for 8 s. | Success ≥ 99%; p99 latency ≤ 100 ms (ingest) |
| Database 5× slower | At 5 s the main database on the request path answers 5× slower for 8 s. | Success ≥ 99%; p99 latency ≤ 30 ms (ingest); p99 latency ≤ 50 ms (query) |
| A server dies | At 4 s one server of the first app service on the request path dies for 10 s. | Success ≥ 99% |
| Budget: $3,800/month | The normal day's design must cost at most $3,800 a month. | Cost ≤ $3,800/month |