https://stackoverflow.com/questions/48993286/is-it-possible-to-route-traffic-to-a-specific-pod?rq=1
You can guarantee session affinity with services, but not as you are describing. So, your customers 1-1000 won't use pod-1, but they will use all the pods (as a service makes a simple load balancing), but each customer, when gets back to hit your service, will be redirected to the same pod.
Note: always within time specified in (default 10800):