App Check / 05 Juli 2020

Applies App Check - Corona-Warn-App

App Check

As of today, the federal government's new Corona warning app is available for download throughout Germany. As Liechtenstein's leading specialist agency for customer-centric digital transformation, we took a closer look at the app, whose code has been revealed by the developers from Telekom and SAP.

Overall, we rate the implementation of the app as successful. Of course, there is potential for optimization - however, a large number of valuable improvements by the open source community have already been taken into account in the last few days, resulting in a significant improvement of the code.

#CoronaWarnApp in quick check - iOS implementation.

We are convinced by the implementation of the iOS app in terms of UI, architecture and security. Especially the technologies and tools used, which are very similar to our best practices and state of the art, we rate as positive. The rapidly growing number of automated tests as well as the optimization of the code in response to community feedback are also positive. Critically, we see the lack of use of dependency injection (essential pattern to reduce dependency between objects/classes), which complicates long-term maintainability along with other architectural decisions. Translated with (free version)

#CoronaWarnApp in quick check - Android implementation

We also rate the Android version of the Corona Warning app as functional and without any major flaws. However, we found deficits in the architecture and structure, especially with regard to the SOLID principle. In addition, state of the art and best practices in the development of Android apps (e.g. dependency injection) were partially omitted, which we cannot understand. As a result, the inclusion of other compatible tracing frameworks (e.g. Translated with (free version) Contact Shield Huawei) unecessarily complicated. Tests have been implemented, but they partly lack depth and meaningfulness. The insufficient structure of the Android app causes unnecessary complexity in our opinion.

#CoronaWarnApp in quick check - UX/UI Design

The user interface of the app for iOS and Android is clear and contemporary, and the dark mode was also taken into account. Both platforms ensure - as far as recognizable - accessibility of the app, including dynamic font size and VoiceOver. When analyzing the app from a user experience point of view, its heavy text load is striking. Onboarding already contains a lot of text, which - also due to the missing feedforward information (prediction of how many views are still to be read) - can easily lead to user abandonment. The design of the Corona warning app is done as a one-pager and accordingly does not use a burger menu or tab bar / bottom navigation bar, which could lead to difficulties in navigation for some users. Here we lack a clear navigation structure, which will be of particular importance in future further developments as well as the integration of new features.


In our opinion, the app is convincing in terms of data protection and functionality; minor architectural weaknesses will not interfere with the release of the first version. In view of the manageable development time of 30-40 days, we also consider the total costs estimated by Telekom and SAP in the amount of 20 million euros for absolutely oversized. Against the background that important preliminary work has already been carried out by the DP-3T project were done and the core functionality of contact capture is realized via interfaces from Apple and Google, the actual in-house software development effort is very manageable.

Open questions that need to be clarified from our point of view:

  • When will users of Huawei Devices get the options to install the app?
  • Are there plans to also allow health care representatives, including physicians and health department staff, clinicians, etc., to report confirmed cases of Covid-19 infection to reduce the risk of infection?

The next few days and weeks will show how many users actually install the Corona warning app and what benefit it can ultimately have.