The outage was caused by a hardware failure. Due to the failure, the hypervisor stopped connectivity for the VMs running on the troubled machine. The machine was taken out of the cluster by our DevOps team.
One of the VMs on the server was critical for the overall operation of the cluster, thus impacting its availability. We will be making changes in the product to allow dynamic rerouting to any available replica.
I apologise for the inconveniences this has caused.