Deployment failed - Too many backends

We’re trying to add more backend services to XDN for routing, but we are unable to.
We get an error:
failed with 400: Too many backends, found 17 and only 15 are allowed

Is this a hard limit?
Do we need to maintain multiple layers of proxies and routers?

This is a hard limit on the v3 system. V4 does not have this limit.