Editing Personal Data Server (PDS) (section)

=== Repository Hosting and Management ===
The primary function of a PDS is hosting and managing public AT Protocol repositories. The PDS maintains the [[Merkle Search Tree (MST)]] data structure that stores user content, handling mutations and generating [[diffs]] between repository versions. These diffs are streamed as real-time updates to [[Relay|relays]] via [[wikipedia:WebSocket|WebSockets]], allowing the network to efficiently aggregate and broadcast updates to user repositories.

The PDS validates all records against their [[lexicon]] schemas before adding them to the repository to ensure data integrity. It also provides a repository [[event stream]] that notifies subscribers of changes, including sequence numbers for ordering and a backfill period for catching up after disconnections.

For data portability, the PDS supports importing and exporting repositories as [https://ipld.io/specs/transport/car/carv1/ CAR files], allowing users to migrate between providers without losing their content or social connections.