Version-Barrier Read Routing Diagram

Primary routing

Own-data reads go to the leader: always fresh, always costs leader load
Use it for the keys the user just wrote, not for everything
After the primary fails, this route depends on replication durability

Version barrier

The client remembers last-write LSN 7; only replicas past it may answer
Needs LSNs or version vectors on reads, not wall-clock sleeps
When no follower qualifies, the dashed fallback reads from the leader

Session stickiness

Pinning each session to one replica stops time moving backward
It does not give read-your-writes after a write elsewhere
Re-pin explicitly on replica failure; a silent move can regress