System designMediumsd-g216

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

Question

Design graceful failover for a product-detail page service whose page depends on 6 downstream services (pricing, inventory, reviews, recommendations, images, personalization). The page is the top revenue driver and must keep rendering even when a downstream is slow or down — but pricing and inventory are correctness-critical while reviews/recommendations/personalization are nice-to-have. How do you isolate failures so one slow dependency can't take down the page, and what does 'degraded' look like?

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.