S3 · E5 · 2025
Ninety-Nine Problems and a Cache
A dashboard takes four seconds to show anything. The team wants a rewrite. Ida has two weeks and a whiteboard.
Client: Lumen Analytics · Performance
Previously on…
Lumen's customers open their dashboard on old laptops in slow offices. The app had grown into one big bundle and the first chart took four seconds. The team wanted it fast without a rewrite and without stopping work on new features.
Guest star
“We were ready to rewrite everything. She drew some boxes and deleted half our bundle.”
The episode
Cold open. A sales call. The client clicks the dashboard. Everyone watches a spinner for four long seconds. Roll titles.
Act one
Ida measured before touching anything: a week of real-user data and the same three journeys on a throttled laptop. Most of the four seconds went into code the first screen never used.
Act two
The bundle was split by page and then by panel. The chart library loads with the first chart, the map only when someone opens it. A performance budget now runs in CI and fails a pull request that adds more than 20 kB.
The tag
The whiteboard is still in the office. Nobody has dared to wipe it.
Scenes
Day nine. The cat found the slow query. Nobody believes this.
How it ended
- First chart
- Before: 4.1 sAfter: 0.9 s
- JavaScript on first load
- Before: 2.1 MBAfter: 380 kB
- Support tickets about speed
- Before: 12 a monthAfter: 1
Crew
- React
- TypeScript
- Vite
- Vitest
