Primary and replica

[imacks]

Hello maintainers,
I would appreciate clarification on the primary/replica setup. From what I gather, there should be a single primary only. Any number of replicas that would download the token store from the primary on start.
Say I enable writable token store on both primary and replicas. The primary is at primary example com, and many replicas are behind a loadbalancer at replica.example.com. The loadbalancer uses simple random routing. What happens if i try to upload a token to replica.example.com? Would the primary now contain the uploaded token? In other words, is the primary's sole purpose a source for new replicas to sync up to?