In cosmos DB, one replica-set consists of 4 replicas. It has one leader and 3 followers (including a forwarder).
I assume that all updates go through the leader first and the leader is the first one to be updated when updates come in the replica-set.
If my assumption is correct, a reader does not have to read many replicas. It only needs to check the leaders in each replica-set to figure out latest updates.
For example, Cosmos DB documentation says that in case of eventual and consistent prefix consistency models, quorum reads is accessing one single replica. As far as I understand it, the single replica can be any replica in a region. But, if a reader needs to read a update from a replica, does it have to be a leader replica?
For read operations on Eventual consistency, it can be any of the 4 replicas that are available, so the read will land on any of them, not particularly the leader.