Building reliable (and fast) directory sync

Directory sync is the process of copying an organization's user and group information from identity providers like Okta or Entra into applications and keeping it synchronized as changes occur. Firezone chose to build its own directory sync engine from scratch rather than use the leading standard, because implementing it reliably and quickly is more complex than it initially appears. The system must continuously track three types of changes—new users and groups, updates like name changes, and removals—while maintaining access control based on group membership.