FrontendHaltPerformance·Intermediate·Conceptual·1 min read
Why can a good Lighthouse score coexist with poor real-world INP?
Short interview answer
Lighthouse measures a simulated load and a limited set of interactions in a lab. Real users trigger interactions Lighthouse never tests, on slower devices, with more background work, so field data (from the Chrome UX Report or a RUM tool) is the authoritative INP source.
Key takeaway
Explain the underlying mental model clearly, then support it with a concrete example and its trade-offs.