A week ago we posted an incomplete postmortem and are now following up with the completed version. If you want the full story of how we progressed through this incident, start by reading that. This postmortem will cover the full root cause analysis but it won’t rehash the first part of the investigation.
Edit February 26, 2018: We have just posted an updated and complete postmortem here: https://devblogs.microsoft.com/devopsservice/?p=16295
On 7 February 2018 we had an incident which impacted users in our Western European scale unit. During this time, users experienced slow performance and 503 errors (service unavailable) when interacting with VSTS services.