System designHardsd-g171

Subject Slo monitoringLevel Senior–Staff~40 minCommon in Reliability & on-call · Code quality & review interviewsIndustries Technology, Software development

Question

Design SLO monitoring for a user-facing service whose request depends on 6 internal microservices and 2 external vendors (a payment processor and an email provider). The product team owns a 99.9% end-to-end SLO but each dependency has its own SLO and its own owner. You need to (a) measure the true user-experienced SLO, (b) attribute budget burn to the dependency that caused it, and (c) catch failures even during zero-traffic periods. Design the SLI measurement, dependency attribution, and synthetic coverage.

What a strong answer looks like

Clarify scale and constraints first. Propose a clean component breakdown, then go deep on the hard parts — data model, bottlenecks, consistency, failure modes — and name the trade-offs you are making.

Learn the concepts

Narrate your design

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Run or narrate your approach, then ask the coach.