https://www.techradar.com/news/xbox-one-july-update-halves-download-times

Downloading a game from online storefronts like Steam or the Xbox Live Marketplace is the modern equivalent of waiting for your modem to connect to the internet circa 1998: They’re both long, arduous processes that we all know can happen much faster than they do. 

The good news is that just like broadband killed dial-up, Microsoft has introduced a new feature called FastStart that will drastically reduce the amount of time it takes to start a new digital game you’ve just bought.