Earlier quoted context omitted.
The corona app doesn't need to be a huge contract. But SAP and T-Systems can sure waste a huge amount of time and charge a huge amount of money for it.
Developing a tool to be used by 80 million people to help fight a global pandemic under big time pressure is not a huge contract?
The iOS app has 3 main contributors https://github.com/immuni-app/immuni-app-ios/graphs/contribu...
The Android app has one with 50+% of commit https://github.com/immuni-app/immuni-app-android/graphs/cont...
Then there are several backend. All considered it's not a small project but not a large one.