keep corporate app alive in background

I am developing a corporate app that will be publish on an internal store. The app is just supposed to keep in memory some credentials but I can't store them on the device for security reasons.

I want the app to stay in background as long as possible but I don't know what is the best solution knowing that I won't have to publish the app in the AppStore.

I read about the option in plist Required background modes, but I don't know which option is the most efficient for my situation.