[Feature request] individual items expiry

[alex-jitbit]

Item-specific expiry TTL.

Probably by inheriting LruItem and LruItemPolicy implementation that will implement individual expiry for items.

[bitfaster]

There is some sample code here that does exactly what you described: #182.

I will figure out how to do this cleanly in the next major version and have it built in. Adding it now will break the atomic/scoped features, and the time policy property for TTL should be changed to a method that resolves the TTL based on the item.