We’ve increased the max etcd size with the --quota-backend-bytes flag, and the autoscaler now has a sanity check not to take action if it would terminate more than 50% of the cluster.

We then moved the etcd directory for each node to the local temp disk, which is an SSD connected directly to the instance rather than a network-attached one. Switching to the local disk brought write latency to 200us, and etcd became healthy!