ok, I did some progress understanding it.
services-workers.js contains this route:
// dynamically cache any other local assets
If the request matches a cache entry, respond with that. Otherwise try to fetch the resource from the network. If the network request succeeds, update the cache. This option is good for resources that don't change, or have some other update mechanism.
I'm using ionic2 only for PWA. I've removed Cordova and I'm deploying the www folder, generated with build --prod, simply copying it into my CDN.
How does the service worker know when I deploy new files ?