Nodes in Azure Database for PostgreSQL – Hyperscale (Citus)

The Hyperscale (Citus) hosting type allows Azure Database for PostgreSQL servers (called nodes) to coordinate with one another in a "shared nothing" architecture. The nodes in a server group collectively hold more data and use more CPU cores than would be possible on a single server. The architecture also allows the database to scale by adding more nodes to the server group.

Coordinator and workers

Every server group has a coordinator node and multiple workers. Applications send their queries to the coordinator node, which relays it to the relevant workers and accumulates their results. Applications are not able to connect directly to workers.

For each query, the coordinator either routes it to a single worker node, or parallelizes it across several depending on whether the required data lives on a single node or multiple. The coordinator decides what to do by consulting metadata tables. These tables track the DNS names and health of worker nodes, and the distribution of data across nodes.

Next steps