Attach Persistent Volume for Durable Files vs. Keep Service Stateless with External State: Which Limits Scalability?

Goal: Identify the real bottleneck before scaling

Railway dashboards expose per‑service CPU, memory, and network usage. Before resizing an instance or refactoring code, you should confirm whether the application is throttled by CPU, memory pressure, or disk I/O.

Trade‑off: Persistent Volume vs. Stateless Service

Attaching a volume guarantees that files written at runtime survive redeploys, but the platform limits the service to a single replica. A stateless design keeps the container filesystem temporary and allows multiple replicas, but any required state must be moved to an external database or object store.

Unresolved decision: does the app write local state that must persist across deploys? If yes, the volume path is the documented route, yet it sacrifices horizontal scalability. If no, you can remain stateless and scale out.

• Will the application store user uploads or a local cache that must survive restarts?
• Does the current plan allow more than one replica when a volume is attached?
• What is the cost of cleaning stale files when using a persistent volume?