AWS RDS Writer Endpoint vs Reader Endpoint
An aurora cluster instance might be either a writer or a reader. Aurora clusters allow one writer and up to 15 readers. The instance role might change failover happens.
The writer DNS endpoint always resolves to the writer instance,Cluster writer endpoint
The reader endpoint DNS randomly resolves to one of the reader instanceswith TTL=1.
(Note: It might point to the writer instance only if they are one healthy instance is available in the cluster fleet)Cluster reader endpoint