nats-serverstop it and restart it with JetStream enabled using
nats-server -js(if that's not already done)
nats kv add <KV Bucket Name>:
nats kv del my_kv Key1
nats kv watch my_kv: this will start a watcher on the bucket we have just created earlier. If you followed this walkthrough the last operation that happened on the key is that it was deleted. Because by default the KV bucket is set with a history size of one (i.e. it keeps only the last change) and the last operation on the bucket was a delete of the value associated with the key "Key1" that is the only thing that get received by the watcher:
nats kv watchrunning and in another window do another 'put'