Don't be surprised if this question pops up as one of the top OpenStack interview questions in your next interview. Cell lets us scale an OpenStack Compute cloud in a distributed way without relying on complicated technologies, such as database and message queue clustering, thus making it a preferable choice for large deployments. Once we enable this functionality, it will partition the hosts in an OpenStack Compute cloud into groups called cells. These are configured as a tree with the top-level cell having a host running the nova-api service rather than nova-compute. Whereas the child cells can run nova-* services except nova-api. We can consider a cell as a Compute deployment where each cell has its database server and message queue broker. The nova-cells handle communication between cells via RPC and select cells for new instances. Cell scheduling is different from the host schedule. The nova-cells select a cell whose request will be sent to the nova-cells service and then to the host scheduler and stats building. These cells are disabled by default, and we need to enable it explicitly by setting “true” to its functionality.