A request to initiate a launch procedure of a compute instance at a virtualization host configured to access a remote storage device over a network is received. A memory buffer of the host is allocated as a write-back cache for use during a portion of the launch procedure. In response to a write request directed to remote storage during the portion of the launch procedure, the write payload is stored in the buffer and an indication of fulfillment of the write is provided independently of obtaining an acknowledgement that the payload has been propagated to the remote storage. Subsequent to the portion of the launch procedure, payloads of other write requests are transmitted to the remote storage device.