Move Less, Move Faster: Speeding Up Citus Cluster Scaling

Scaling a distributed Postgres cluster often isn’t limited by “adding a VM”, it’s limited by how long it takes to rebalance data safely. In this talk, I’ll give a minimal mental model of how Citus distributes data (shards, placements, and coordinator/worker roles), then explain why cluster scaling can feel painfully slow: data movement is expensive, and concurrency is constrained by safety and resource limits.

We’ll then look at two concrete steps toward faster elastic scaling:

Shard rebalancing improvements that increase parallelism and reduce bottlenecks.

Snapshot-based node addition, where a new worker starts as a clone of an existing one, dramatically reducing how much data needs to be copied during rebalancing.

Attendees will come away with a clearer way to reason about scaling time, plus actionable guidance for running scale-out/scale-in events safely.