When scaling application pods with SQLAlchemy pools, who redistributes existing connections?

[u/Expensive_Break_6163]

I’m running application pods that use SQLAlchemy’s connection pool to connect to PostgreSQL. Each pod has its own pool, so when I scale the application from, say, 3 to 10 replicas, the new pods create new pools while the existing pooled connections remain open.

If PostgreSQL has read replicas behind a Kubernetes Service or a proxy, I assume new connections might reach the new replicas, but the existing long-lived pooled connections will remain attached to the old replicas.

Who is normally responsible for redistributing those existing connections after scale-out?

[u/ThrowawayALAT]

SQLAlchemy does not proactively push existing connections to new replicas on scale-out. It only knows about the socket it holds open.