Final Update: Thursday, 15 February 2018 19:50 UTC
We have been able to isolate the issue to a network hardware power event in Azure West Europe data center. We will work with our partners in Azure to understand the detailed root cause analysis.
More details on the power event can be found at: https://azure.microsoft.com/en-us/status/history
Update: Thursday, 15 February 2018 16:44 UTC
We were alerted to an increase rates of 503-Service Unavailable errors in West Europe region. Initial investigation points to an unhealthy database which was impacting various feature areas within VSTS.
The problem began at 15 February 2018 15:46 UTC and is mitigated as of 15 February 16:16 UTC. We are still engaged on the bridge working to understand the root cause.