What is the minimum number of nodes needed to form a functioning cluster?

The minimum number of nodes for a functioning cluster depends on the cluster type and the technology used, but generally:

• For a fault-tolerant cluster with leader election (e.g., in Kubernetes or database clusters), at least 3 nodes are required. This is due to the need to achieve quorum for consistency.

• For a simple cluster without high availability requirements, 2 nodes can be used.

• In some cases (e.g., for development or testing), a cluster can be run with a single node, but it will not be fault-tolerant.

Thus, a fully functional fault-tolerant cluster usually requires at least 3 nodes.