Free AWS Cloud Practitioner CLF-C02 Practice Question
Amazon EC2 instances that are deployed within the same availability zone do not generate data transfer fees, provided they communicate over the network path reserved for local instance-to-instance traffic.
When Amazon EC2 instances are located in the same availability zone and use the network pathway designated for local (or internal) traffic, data transfer fees are not applied. This is because the traffic is contained within the same physical infrastructure and does not move out to different data centers or over the public internet.