How the Workers help to ultimate a site

Hi,

Right now my client has a brilliant response time and load on their site, they use Cloudflare services and they have implemented caching on their servers, backend code and also use Varnish. I basically have two questions:

  1. Under the previous explanation, what additional advantages or what could be improved on the site if Workers are implemented?

  2. With a worker can I have Background Sync?