You need to run both old and new API versions behind the same SSL and DNS records so new customers can try the revision while keeping the old API deployable. What should you do with the load balancer?

The correct approach is to use separate backend pools for each API path behind the load balancer. This allows you to route traffic for different API versions (e.g., /v1/api and /v2/api) to distinct sets of backend instances, all while using the same SSL certificate and DNS record. This enables A/B testing or gradual rollouts to new customers without impacting existing ones. Configuring a new load balancer for the new API version would require a new DNS record or complex DNS routing, defeating the purpose of using the same SSL and DNS. Reconfiguring old clients is not feasible for a seamless transition and would break existing integrations. Having the old API forward traffic to the new API based on the request path adds unnecessary latency and complexity to the application layer, rather than handling it efficiently at the load balancer level.