Fastly is a cloud computing services provider. Fastly's cloud platform provides a content delivery network, Internet security services, load balancing, and video & streaming services.
GitHub Pages is a static site hosting service.
Polyfill is a service which accepts a request for a set of browser features and returns only the polyfills that are needed by the requesting browser.
Priority Hints exposes a mechanism for developers to signal a relative priority for browsers to consider when fetching resources.
Varnish is a reverse caching proxy.