DataTransfer-Regional-Bytes High Costs

Question

Hi,

We have some unusual activity regarding DataTransfer-Regional-Bytes costs (EC2-Other), specifically "InterZone-In" and "InterZone-Out" costs. Starting from some infra changes we see high charges in daily usage, as high as $400 per day.

Our only infrastructure change is that we are not using "terraform apply" (GitHub Actions now). This terraform code is configuring ECS task definition, ECS Service, Cloud Map Namespace, LB Target Group and LB Listener Rule per client. Our previous expenses were around $20 per day.

Do you have some guidelines how to approach in investigating this issue, or some basic idea what it could be?

Thanks in advance

Accepted Answer

InterZone-In and InterZone-Out are cross AZ data transfer costs. We often see this in containerized workloads when each POD is Multi-AZ, when the communication from 1 POD to another can cross AZs, then you can end up with this ping-pong type affect of traffic crossing back and forth between AZs.  I suspect this is what you are seeing.

The only way I know of to limit this is to only have the Multi-AZ aspects of the workload at the ingress LB and the data store (DB?) and have each AZ deploy a set of PODs. This requires that the workload activity would be quick enough such that on a retry and timeouts if an AZ were to fail, the client would quickly try again and the next request would go to another AZ. You would still have some cross-AZ traffic at the LB and DB layers, but the POD to POD communications would all be in the same AZ.

Answer

Hi, do you have an ECR in each region with replication of container images for ECS? That may be a source of trafic

DataTransfer-Regional-Bytes High Costs

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