Most people associate a lack of reliability with anything Microsoft-related. Although I do not think that is the cause of Gitlab's problems.

Reading their Twitter status messages. Microsoft sponsored Azure for Gitlab. Between Oct and Dec they were on Azure, and they had major issues with the Azure platform, pretty unreliable for their use case. Gitlab switched to IBM Softlayer because of that experience. Read yourself: https://twitter.com/gitlabstatus and https://gitlab.com/gitlab-com/operations/issues/17

Although we planned to switch to Softlayer we're still on Azure. It has given us a hard time, but in the last few weeks things have gotten more stable. Our availability is better (fingers crossed) but our speed is still unacceptably slow https://gitlab.com/gitlab-com/operations/issues/42

From first hand experience, Softlayer has been nothing but fantastic to us over the last few years, and cost effective.

Thanks, so far we're really happy about Softlayer.

It seems they have switched back to Azure now. In my own (very limited and small-scale) experience, Azure is pretty solid. Although some of the APIs seemed a bit unnecessarily convoluted compared to AWS (can't recall any specific instance).