February 14, 2025

The Factory: Building Azure DevSecFinOps at Scale

The Problem: “We need to deploy 10 new regions next month.”

In the world of traditional infrastructure, this sentence is a death sentence. It typically means 30 days of copy-pasting code, drift, and manual “click-ops” to fix the gaps.

At Kyndryl, facing this exact challenge for a global banking client, we realized that “writing Terraform” was the bottleneck. We needed a paradigm shift. We didn’t just automate the infrastructure; we built a Factory.

The Philosophy: Engine vs. Fuel

Most engineering teams struggle with IaC scaling because they mix their Logic (Terraform Resource Blocks) with their Data (Variables/TFVars). When a new region is needed, they copy the entire folder structure, effectively forking their own codebase.

We adopted a manufacturing principle: The Engine (Code) must be immutable. The Fuel (Data) defines the output.

  • The Engine: A set of generic, hardened Terraform Modules (modules/network, modules/aks).
  • The Fuel: A single, human-readable YAML Configuration file (config.yaml).
  • The Product: A fully compliant, secure Azure Landing Zone.

2. Core Components

The Single Source of Truth (config.yaml)

We banished .tfvars files. They are developer-centric and hard to validate structurally. Instead, we used YAML, which allows us to define nested structures (Spokes -> Subnets -> NSGs) in a way that visibly maps to the topology.

# config.yaml - The "Order" for the Factory
environment: "prod-eus-001"
region: "eastus"

# The Factory iterates over this list
spokes:
  app01:
    cidr: "10.11.0.0/23"
    peering: true
    subnets:
      web: { cidr: "10.11.0.0/26", nsg: "strict-web" }
      db:  { cidr: "10.11.0.64/26", nsg: "strict-db" }

The Engine (main.tf)

Our main.tf became incredibly boring—and that’s the goal. It contains almost no logic. It simply reads the YAML and feeds it into the modules.

# main.tf - The Assembly Line
locals {
  config = yamldecode(file("${path.module}/config.yaml"))
}

module "spokes" {
  for_each = local.config.spokes
  source   = "./modules/spoke-network"

  name           = each.key
  address_space  = each.value.cidr
  security_level = each.value.subnets.nsg
}

3. The Architecture

We realized that “Security” and “Finance” (Tagging) could not be afterthoughts. They had to be part of the assembly line.

graph TD
    subgraph Factory_Inputs
        YAML[config.yaml]
        TF[Modules/Engine]
    end

    subgraph Assembly_Line
        Valid[Validation Layer]
        Sec[Security Injection]
        Fin[Cost Tagging]
    end

    subgraph Output_Azure
        Hub[Hub VNet]
        Spoke[Spoke VNets]
        NVA[Palo Alto NVA]
    end

    YAML --> Valid
    TF --> Valid
    Valid --> Sec
    Sec --> Fin
    Fin --> Hub
    Fin --> Spoke
    Hub --> NVA

    %% Brand Styles - "Cyber-Glass"
    classDef input fill:#0f172a,stroke:#38bdf8,stroke-width:2px,color:#fff,stroke-dasharray: 5 5;
    classDef process fill:#1e1b4b,stroke:#a855f7,stroke-width:2px,color:#fff;
    classDef azure fill:#172554,stroke:#3b82f6,stroke-width:2px,color:#fff;

    class YAML,TF input;
    class Valid,Sec,Fin process;
    class Hub,Spoke,NVA azure;

    linkStyle default stroke:#94a3b8,stroke-width:2px;

4. The “DevSecFinOps” Trinity

This Factory approach allowed us to solve three problems simultaneously:

1. Security (DevSecOps)

We embedded Palo Alto NVA requirements into the hub-network module. A developer cannot deploy a Hub without the NVA, because the module requires the NVA parameters to function. Security is no longer a policy; it’s a dependency.

2. Finance (DevSecFinOps)

We mandated that the config.yaml must contain a cost_center key. The Terraform locals block merges this tag into default_tags. Every single resource—from a VM to a public IP—inherits this tag. We achieved 100% Cost Visibility overnight.

3. Operations (DevSecFinOps)

When we needed those 10 regions, we didn’t write code. We wrote a script to generate 10 unique config.yaml files. The deployment took 4 hours.

Key Takeaway

If you find yourself writing the same resource "azurerm_virtual_network" block more than twice, stop. You aren’t engineering; you’re typing.

Build a Factory. Move the complexity into the Engine, keep the Fuel simple, and let the assembly line handle the scale.

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