When users sign up for Instagram, they are asked to fill out some basic details. While this is going on, in the background, Instagram starts looking for recommendations on who to follow.
The result is that by the time the user submits the form with their account information, recommendations are presented nearly instantly.
Instagram uses the same trick on image uploads. After you select the filter for your image, you can choose options such as where to share the image, or geotag it with a location. All the while, Instagram is already uploading the image in the background to reduce the time users have to wait at the end of the process.
It is worth noting that in both of the cases, there's a very high likelihood that ...