Cloud Cost Optimization and Financial Operations Questions

variable "env" {
  type    = string
  default = "dev"
  validation {
    condition     = contains(["dev","staging","prod"], var.env)
    error_message = "env must be dev, staging, or prod."
  }
}

variable "requested_instance_type" {
  type = string
  validation {
    condition = (
      var.env == "dev" ? can(regex("^t[2-3]|t4g", var.requested_instance_type)) : true
    )
    error_message = "Dev only allows burstable (t2/t3/t4g) instance classes."
  }
}

locals {
  default_instance_by_env = {
    dev     = "t3.micro"
    staging = "t3.medium"
    prod    = "m5.large"
  }

  instance_type = coalesce(var.requested_instance_type, local.default_instance_by_env[var.env])
}

resource "aws_instance" "app" {
  ami           = var.ami
  instance_type = local.instance_type
  tags = merge(var.tags, { Environment = var.env })
}

output "infracost_resources" {
  value = [{
    name         = "aws_instance.app"
    instance_type = local.instance_type
    region       = var.region
    quantity     = 1
  }]
  sensitive = false
}

package terraform.iac

deny[msg] {
  input.resource_changes[_].type == "aws_instance"
  input.resource_changes[_].change.after.tags.Environment == "dev"
  startswith(input.resource_changes[_].change.after.instance_type, "m5")
  msg = sprintf("Disallowed instance class %v in dev", [input.resource_changes[_].change.after.instance_type])
}

- uses: actions/checkout@v4
- uses: infracost/infracost-action@v2
  with:
    command: comment --path plan.out --threshold 50
- run: terraform plan -out=plan.out
- run: infracost breakdown --path plan.out --format json --out-file infracost.json
- run: conftest test plan.json

SELECT
  -- month as 'YYYY-MM' (adjust formatting functions per SQL dialect)
  CAST(EXTRACT(YEAR FROM month_start) AS VARCHAR(4))
    || '-' ||
    LPAD(CAST(EXTRACT(MONTH FROM month_start) AS VARCHAR(2)), 2, '0') AS month,
  service,
  SUM(cost) AS total_cost
FROM (
  -- normalize timestamp to first day of month
  SELECT
    service,
    cost,
    CAST(DATE_TRUNC('month', usage_start) AS DATE) AS month_start
  FROM billing
  WHERE usage_start >= (CURRENT_DATE - INTERVAL '12' MONTH)
) t
GROUP BY month_start, service
ORDER BY month_start DESC, service;