We are hosting a stateful card game server on Railway and releasing updates frequently. We rely on a graceful shutdown strategy to ensure active games are not interrupted.

Our Setup & Logic:

1. We listen for SIGTERM on the old deployment.

2. Once received, we stop accepting "Create Room" requests but keep processing logic for existing rooms.

3. We set a 1-hour timeout to allow players to finish their current games.

4. We have configured:

* RAILWAY_DEPLOYMENT_OVERLAP_SECONDS: 3600

* RAILWAY_DEPLOYMENT_DRAINING_SECONDS: 3600

The Problem:

Even with the overlap settings, it appears that all incoming traffic is routed to the NEW deployment immediately once it becomes active. This breaks our game logic because players currently in a game (hosted on the OLD deployment) send requests that are being routed to the NEW deployment, where their game session data does not exist.

Our Question:

During the OVERLAP_SECONDS period, how does Railway handle traffic routing? Is there a way to ensure the OLD deployment continues to receive traffic (or enable sticky sessions) so existing players can finish their games?

We need the old deployment to remain publicly accessible via the domain until it shuts down safely.