Questions about Active PD Follower

Active PD Followe of version 8.5.0 PD module is officially GA, which improves PD's high concurrent request processing capabilities and makes the performance of the entire TiDB cluster more stable. But there is a question, how does the client communicating with the PD Follower determine that the information obtained from the PD, for example, the region is the latest (same as the leader). Can you explain the request process and processing logic in this area? Thanks!