An Xplenty cluster is a group of machines (nodes) that is allocated exclusively for your account's users. You can create one or more clusters, and you can run one or more jobs on each cluster. A cluster that you've created remains allocated to your account until you request to terminate the cluster.
When you create a new cluster, you can choose from different cluster sizes (the number of nodes) according to the computing power you require for different types of jobs and packages (if you have a contract that allows you to do so). Generally speaking, the relationship between the number of nodes and computing power is linear: if a job takes four hours to run a four-node cluster, it will take one hour to run on a 16 node cluster.
All accounts include one free sandbox cluster for testing jobs on relatively small amounts of data during the package development cycle. Since the sandbox cluster is single-node and neither scalable nor highly available, it is not production-grade.
Trial users who haven't signed a contract yet have unlimited access to a sandbox cluster and 30 hours on a single node production cluster during the trial period.