Performance and optimization · Knowing it's fast

Monitoring-style app

Illustrative system design for a knowing it's fast app like Monitoring: 3 topics to read, from requirements to deep dives.

Illustrative design, not Monitoring’s actual implementation. Arrowbox is not affiliated with Monitoring’s owner. Disclaimer

Core

Measuring real usersIntermediate · 44 min read · Sign in to read
Performance observers in the page record LCP, CLS and INP with attribution, and a beacon sent when the page is hidden delivers them; report the 75th percentile, split by device and connection.
Catching errors in the fieldIntermediate · 40 min read · Sign in to read
Global handlers and component error boundaries catch what breaks in users' browsers; source maps turn minified stacks back into code, and grouping, breadcrumbs and scrubbing make reports usable and safe.
Lab data, field data and releasesIntermediate · 36 min read · Sign in to read
Lab tests are repeatable and catch regressions before release; field data tells you what users actually got; a lab gate in CI and a canary compared at p75 connect the two.