How to get subnet IP for specific AZ with CDKTF

I have a subnet declared as follows which creates 4 subnets, one in each of the 4 AZs in us-west-2 in AWS

    const largePublicSubnets = new aws.vpc.Subnet(this, "large_pub_subnet", {
        "${cidrsubnet(aws_vpc.vpc.cidr_block, 4, count.index + 2 * length(data.aws_availability_zones.all.names))}",
      mapPublicIpOnLaunch: true,
      tags: {
        name: environment + "-large-public-subnet-${(count.index + 1)}",
        ["" + eksClusterName]: "shared",
        "": "1",
        environment: environment,
        public: "true",
      vpcId: "${}",
    largePublicSubnets.addOverride("count", Fn.lengthOf(zoneNames));

In addition to this, I have a nodegroup declared as follows, which uses all 4 of the above subnets:

    const firehoseNodeGroup = new aws.eks.EksNodeGroup(
        nodeGroupName: `eksNodeGroup-${environment}-firehose`,
        nodeRoleArn: nodeGroupRole.arn,
        subnetIds: [],
        instanceTypes: ["m5.4xlarge"],
        labels: {
          app: "firehose",
        scalingConfig: {
          minSize: 0,
          maxSize: 4,
          desiredSize: 1,
        dependsOn: eksNodeGroupRoleAttachments,
        tags: {
          Name: "firehose_eks_node",
        lifecycle: {
          ignoreChanges: ["scaling_config[0].desired_size"],
        taint: [
            key: "app",
            value: "firehose",
            effect: "NO_SCHEDULE",
      "${ [ aws_subnet.large_pub_subnet[0].id, aws_subnet.large_pub_subnet[1].id, aws_subnet.large_pub_subnet[2].id, aws_subnet.large_pub_subnet[3].id ]}"

I’d like to restrict my node group to only run in one specific AZ, us-west-2c, but I’m not sure how to correctly determine which subnet corresponds to that AZ. How can I do that? I’m open to redesigning my subnet declaration if needed since the current structure is some tech debt we’ve accumulated.

If you are open to restructuring, the simplest code would be to not use availability zones data source and instead just have them as a configuration. That way you would be able to simply create them in a way that you know which one is which.

You could probably chain a couple terraform functions together to filter the list down to just the one subnet you are looking for. I don’t have a working example of that though.

Got it. Yeah I figured manually making subnets for each AZ instead of using iterators and such with terraform would end up being easier. Thanks for the confirmation!