After deploying the latest release an environment variable was missing that the release had introduced and was dependent on.
Narrowing the bughunt to the particular environment variable produced a different environment variable bug, that proved even harder to identify.
Scrambling all resources we finally found the final environment variable set, that was error free and operations resumed normal state.
The total downtime was approx. 25 minutes.
We are sorry for this mishap and are working on ensuring that a similar error will not happen again