Q: You have a Terraform configuration that manages resources in 3 AWS accounts. How do you structure this?

Use multiple provider configurations with aliases or split into multiple workspaces/modules: Better approach at scale: separate Terraform root modules per account. Each module has its own state file, backend config, and runs independently. Avoid cross-account state dependencies — they create tight coupling. Use Terragrunt to DRY (Don't Repeat Yourself) across multiple root modules.

provider "aws" {
  alias  = "account-a"
  assume_role {
    role_arn = "arn:aws:iam::111111111:role/terraform"
  }
}

provider "aws" {
  alias  = "account-b"
  assume_role {
    role_arn = "arn:aws:iam::222222222:role/terraform"
  }
}

resource "aws_s3_bucket" "a" {
  provider = aws.account-a
  bucket   = "my-bucket-a"
}