If you play Warframe on PC then from time to time you will have the chance to optimize your download cache. Very occasionally, the game will do this automatically after you start up the launcher. It will usually occur after a substantial update has been made to the game.
By optimizing your download cache, you give the game permission to remove unused assets from the game files, improving things like loading times as the game has less information it needs to read through to get to the information it wants at any given moment.
How long does it take to optimize the download cache?
This is really down to a number of variables. If someone has been doing it each time the option becomes available, then it should be a shorter process than someone who has never taken the chance to do it before. Other factors will impact the length of time it takes, such as the type and speed of the drive you have installed the game on. HDDs will simply take longer than SSDs due to the difference in write speeds. Finally, your internet connection will play a role, as the game can only shuttle information to your computer as fast as your connection will allow.
Do I have to do it?
For optional ones, no. If you are in a rush to play, like you are worried about not getting the daily Sortie done before reset, you can simply skip it and it should still be an option the next time you start up the game. From time to time, however, Digital Extremes will push an update that automatically starts the process for you the same as any other update.
Occasionally, the process might hang, and you will not notice any progress on the counter for some time. If this happens we have found that simply restarting the launcher will get things moving in the right direction again.