How to provide static elastic IP to ECS Farget service (web application) to connect databases in other VPCs for outbound traffic and inbound traffic for general users as HTTP/HTTPS requests?

Hello. You can try use ALB instead NLB it`s it is more suitable for use together with ecs https://docs.aws.amazon.com/AmazonECS/latest/userguide/create-application-load-balancer.html

Best regards, Andrii

Is there any way to assign a static elastic IP to the ECS Farget service or CIDR block with a range of IPs that can work?

No, ECS currently doesn't support Elastic IP, you can only have an auto-assigned public IP. Moreover, an Elastic IP is assigned randomly and cannot be specified with CIDR range either.

I have a web app in ECS Farget and I need to connect databases in other VPCs as outbound traffic

However, if you simply need a static IP because you need it to be within a CIDR range to have it allowed by a certain security group's inbound/outbound rules, you can simply use a inbound/outbound rule that allows a certain source/destination security group (e.g.,, the one that is attached to your ECS Service) instead of CIDR IP block.

I read this answer how-to-use-elastic-ip-for-aws-ecs-with-farget-without-using-network-loadbalancer but cname records cannot be used for adding as IPs.

No, CNAME records cannot have a static IP as value. Instead, you need to either use CNAME record and set its value to LB's domain name, or use A record and set its value to the static IP or alias if the target service supports it.