Configure Redis to fire expiry events for only a set of keys

I need to use Redis in the pub/sub mode. I have a subscriber which listens to the expiry events on a particular key.

For this I use: CONFIG SET notify-keyspace-events xK

With the above config, Redis will publish expiry events for all the keys. This has a performance overhead.

I need to make sure that redis emits expiry events for a certain set of keys(configurable).

Please let me know how to implement this