TL;DR

I wanted to operate pages that require Google login from n8n via Playwright MCP

The sidecar approach is easy, but has gaps from the perspectives of authentication and team isolation

I built defense-in-depth with ingress: internal + IAM (roles/run.invoker) + service-to-service auth via ID tokens + a Go auth-proxy + Secret Manager

For stateful MCP, set maxScale=1 to stop scale-out and prevent sessions from jumping to another instance