One of the most important features of HTTP/2 is multiplexing. Multiplexing is the ability to send multiple HTTP requests and receive multiple HTTP responses asynchronously through a single TCP connection, as shown in the following diagram:
HTTP/1.1 does not support multiplexing, which is what led to the various workarounds to improve performance. With HTTP/2, we should no longer be concatenating files into a small number of large bundles. The expensive cache invalidation of a bundle that is necessary when any of the files in the bundle are changed can now be avoided or minimized. We can now transfer more granular assets, either by not bundling at all or having an increased number of bundles, where each one contains a small number of related files rather than just a few bundles containing many. A more granular approach allows us to provide an optimal cache policy for each individual file or bundle, maximizing the amount of content that is coming from our cache.
Another technique that is no longer necessary with HTTP/2 is domain sharding. Through the use of multiplexing, we can download multiple assets at the same time using a single connection. The overhead for each shard, which may have been worth it with HTTP/1.1, is no longer necessary.