Just to confirm I understand this..
I write k=val1 at T=2000. This goes to the range lease holder (leader of the raft group).
Before the commitIndex of raft is propagated to the follower raft replicas, I issue a read request,
read k, ReadAtTimestamp T=2000.
This request is served by the follower, which had a clock drift > 1000, so its HLC is well past 2000, and it will serve the request. But no val1 is not available in the store.
So the issue is about clock drift across leader and follower of same raft group (or replicas for same key range)?