Request for Valkey to support sending key and value both on TTL expiration event notification

[guptankita22]

The problem/use-case that the feature addresses

We have the following use case: Every time a certain key expires, we need to get notified and do something, based on it's value. But when redis fires the expired event, the key was already removed from the db when we try to access it later on, which is expected of course. Sometimes it's useful to do something based on value once an expire notification is received, but at this point key (and value) is deleted and there is no way to get this expired value. Can we please have this functionality added in Valkey as additional feature?

Description of the feature

Valkey would send the value along with the key which is expired on TTL expired event notification

Alternatives you've considered

None

Additional information

None

[hpatro]

Thanks for sharing the use case @guptankita22. The risk I see with emitting out the value in the keyspace notification is it would be too bulky and sometimes it might not be feasible (overall value size can be in GBs).

Wouldn't the underlying database have the value stored ? Upon receiving the keyspace event, can't the application act on the underlying layer? The other possibility is to write your own module to hook onto keyspace events and take action on the server side via https://valkey.io/topics/modules-api-ref/#section-module-keyspace-notifications-api.

I guess this fits into the triggers usecase valkey-io/valkey-rfc#9 (@ranshid).