When are keys deleted

[chris-asl]

As per spec, Kademlia handles migration of keys (e.g. when a new node joins) by doing republishing of <key, value> pairs.

I see republishing has been implemented by the client code of js-libp2p-kad-dht, which is js-ipfs.
So, after a node joins the network, it updates its k-buckets and when the republishing happens it will store values that are close to its key.

But since the new node receives a key, the old one should delete or not republish it.
(In the case where the already-existing node's ID is not within the k-closest IDs with the key.)

Is this deletion or not republishing, implemented somehow in this library or is it the responsibility of the client code?