I am creating a service on ECS which just listens from SQS and do some processing. Its a long running poller. For this kind of service, I don't need a Network Load Balancer, right? For ECS with HTTP server, I normally use NLB and use a health check protocol with a health check endpoint. But here, I am not sure how to do all that if I don't need a NLB.
If you're doing what I think you're doing, you don't need a load balancer at all, just containers that can talk to SQS and get jobs. Unless you need to receive traffic for some reason I can't see why the container should have any ports exposed. ECS itself doesn't care if you have a healthcheck or not, it's just constantly polling the docker service to see if the container is still running.