With a few exceptions detailed in this document, you can make additional changes to the .spec field of the object during any modification process, triggering new operations promptly responded to by the operator.

Hence, to interrupt or rollback the last operation, initiate another operation by reverting the .spec back to its previous state, like this:

kubectl patch --type='merge' pxc polardbx-test -p '{"spec": {"topology": {"nodes": {"dn": {"replicas": 3}}}}}'

Immediately follow it by resetting replicas to 2:

kubectl patch --type='merge' pxc polardbx-test -p '{"spec": {"topology": {"nodes": {"dn": {"replicas": 2}}}}}'

This ensures the stable operation of the PolarDB-X cluster.