Per-replica connection-pool sizing versus Railway PostgreSQL max_connections

Operators seeking to optimize request latency across Railway's horizontally scaled application services and managed PostgreSQL instances must determine how to size per-replica connection pools within the platform's private network boundary.

Railway does not universally inject a connection pooler between replicas and the database, leaving pool management as an application concern. Plan-specific limits on replica counts and egress rules, combined with PostgreSQL's max_connections, create a sizing trade-off where total concurrent connections must remain below the database ceiling while still absorbing burst traffic without introducing queueing latency.

What is the maximum safe pool size per replica given a target replica count and database max_connections? How does concurrent request distribution across replicas affect total connection churn? Should operators deploy a dedicated connection-pooling sidecar on Railway or rely on application-level pool tuning?