I can't share code yet but we are working on potentially open sourcing it. We have a no-build policy, so just raw JS. Using an in-house web component framework similar to LitElement. There is a minimal deploy step that creates a manifest that hashes all files in the repo, and the service worker uses this manifest to determine if a file is cached or not, and serves it up if so. Service workers can intercept network requests so they work great for this. The win here is if you change a couple files, only those files need to be downloaded and cached.