Another big advantage of SSD cache is that it solves the cold start problem of the stateful service. Each cloud VM connects to a SSD that exists independently of the VM. When a cloud VM restarts, instead of fetching all data from the cloud storage, we keep the map affinity, and the VM will try to read from its SSD first. Without a SSD cache layer any in-memory cache miss will result in at least one data read from the cloud storage, which is expensive because cloud storage is on hard drives and the latency variation could be large (usually a few hundred milliseconds or more in the worst case). SSD cache could avoid bursts of requests when VMs restart and improve both latency and throughput.