How do multiple Horizon Connection Server instances in a pod maintain synchronization?

Horizon Connection Server instances keep their data in an AD LDS database, which is automatically synchronized between the Connection Server. AD LDS is a Lightweight Directory Access Protocol (LDAP) directory service that provides flexible support for directory-enabled applications, without the dependencies that are required for Active Directory Domain Services (AD DS). AD LDS provides much of the same functionality as AD DS, but it does not require the deployment of domains or domain controllers. In a Horizon environment, each Connection Server instance has a copy of the AD LDS database and replicates changes to other Connection Server instances in the same pod. This ensures that the Connection Server instances have consistent and up-to-date information about the Horizon resources and user sessions12 References:

Configuring Horizon Connection Server1

Understanding VMware Horizon Services2