Code Room
System designHardsd-g291
Subject Distributed counterLevel Mid–Senior~40 minCommon in Distributed systems interviewsIndustries Technology, Software development

Question

Design a distributed counter store for a global product that tracks per-object metrics (video views, post upvotes, ad impressions) where a few objects receive 500k increments/sec while millions of objects receive a handful, and the same counter is incremented from multiple regions concurrently. Reads tolerate a few seconds of staleness; increments must never be lost and must converge to the correct total. A single row per counter is a write hotspot that will melt one shard. Design the increment and read paths.

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.

Narrate your design
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Run or narrate your approach, then ask the coach.