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Flux Systems cut INP from 280ms to 96ms in two sprints.

Flux Systems builds an observability platform for engineering teams. Their dashboard rendered hundreds of charts on a single page, leading to sluggish interactions. PagePulse's INP breakdown by interaction type helped them pinpoint the slowest event handlers.

Key result

65%

INP reduction

We finally have one source of truth for LCP, INP and CLS across every Next.js route. INP dropped from 280ms to 96ms in two sprints.

Marcus Webb
Engineering Lead, Flux Systems
280ms
INP before
96ms
INP after
18
Routes optimized
2
Sprints to ship

Challenges

  • 01INP on the main dashboard was over 280ms on mid-range laptops.
  • 02No visibility into which event handlers were the slowest.
  • 03Synthetic Lighthouse tests did not reflect real user experience.

Solutions

  • 01Used PagePulse's INP breakdown by interaction type to rank the slowest handlers.
  • 02Set a 200ms INP budget with webhook alerts to the team's incident channel.
  • 03Refactored the 6 slowest handlers to defer non-critical work.

Outcomes

  • 01Cut 75th-percentile INP from 280ms to 96ms across all routes.
  • 02Optimized 18 routes in two sprints using PagePulse's per-route breakdown.
  • 03Improved user satisfaction score from 7.2 to 9.1.

Ready to ship
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