How to persist state across multiple MCP server instances for /api/sse and /mcp/message endpoints?

[junan-trustarc]

I have an MCP server setup. When scaled to multiple instances, the /api/sse endpoint returns a temporary /mcp/message callback URL. But when the client calls this endpoint, the request may hit a different instance that doesn't have the expected state, resulting in a failure.

How can I persist or share state across instances so /mcp/message works reliably in a multi-instance environment?