Metrics questions rarely fail because you picked the wrong metric — they fail because you can't say why that metric represents user value, or you mistake correlation for causation. Exponent's latest 2026 real-interview roundup includes a Meta-style execution question: comments are up but watch time is down, what do you do. Today we break it down with a metric tree, using Facebook's famous '7 friends in 10 days' north star metric as the case study — it found Facebook's growth lever, and it also became one of Silicon Valley's most-cited correlation-causation traps.
Workers Observability is for debugging and request tracing; Workers Analytics Engine is for high-cardinality product events and custom metrics; GraphQL Analytics API is for querying existing Cloudflare product data. Keeping those roles separate prevents logs from becoming a database and keeps billing, monitoring, and product analytics from blending together.
Analytics interviews don't test whether you can write SQL — they test whether you can untangle contradictory signals like 'DAU is rising but advertisers are fleeing.' In a real Google hiring committee debrief, a candidate was rejected for treating 'DAU' as the North Star metric for News — the committee wanted a metric tied to business risk, not the prettiest number on the dashboard. Today we use a metric tree to break down exactly this kind of problem, with the legendary 'Google changed a font color and made a billion dollars' as our case study.
Metrics interviews test whether you can make decisions with numbers, not how much statistics you know. Core skills: north star metric selection logic (why this one and not that one), metric tree decomposition (finding actionable levers), funnel analysis (which step's drop-off is most worth fixing), A/B testing design and pitfalls, and judgment when facing counterintuitive data.
"Adding a Cross-Encoder feels better" is not a scientific evaluation. A/B testing tells you whether a change actually works, how much it helps, and which query types benefit.
No industry standard mandates one RAG evaluation tool. Measure retrieval, generation, and operations separately, then choose Promptfoo, RAGAS, DeepEval, or TruLens for the actual stack.