Zpeed Blog

Service Workers and Performance

How service workers can help a fast static web app without making deployments stale.

Published January 12, 2025. Updated May 22, 2026.

Service workers are powerful for repeat-load performance, offline support, and installable app behavior.

For a static utility site, the cache strategy should be simple: cache stable assets aggressively and revalidate HTML and the service worker quickly.

That balance keeps the app fast while reducing the risk of users getting stuck on old content.

A speedometer is especially sensitive to stale code because location permission, GPS filtering, and unit conversion all affect the user’s live reading. The cached app should never prevent a bug fix or SEO copy update from reaching users.

A useful pattern is to treat scripts and icons as versioned assets, while keeping documents short-lived. If the service worker changes, browsers can pick up the new cache list and replace older assets during the next visit.

Performance work should also include failure states. The page needs to remain understandable when GPS permission is denied, when the signal is weak, or when the browser does not provide reliable speed samples.