From Chaos to Control: How Infrastructure as Code Streamlines Legacy Cloud Takeovers

At Disca, we frequently take over legacy cloud-based systems built by other vendors, especially for our Maintenance Mode (link to MM page) offering. These systems are often created by small engineering teams for small to medium-sized businesses, with little focus on long-term cloud infrastructure maintenance. This lack of foresight poses unique challenges as we strive to fully understand, maintain, and evolve these systems without compromising stability.

In this post, we’ll dive into one of the most effective DevOps practices for streamlining these takeovers: Infrastructure as Code (IaC).

Understanding the Chaos

In 2024, even basic web applications rely on a mix of cloud services to meet functional requirements and user expectations. For example, a traditional web application in AWS might include:

• Application servers on EC2 or ECS
• Database managed by RDS
• A cache layer via Elasticache
• File storage via S3
• DNS through Route53
• TLS certificates from ACM

And that’s just the beginning. Add in IAM configurations, VPC / networking setup, security groups, etc, and suddenly there’s a lot to manage, audit, and evolve. Without IaC, these systems often face:

• One-off changes that get overwritten or missed downstream
• Inconsistent environments, leading to “it worked in staging” scenarios when production fails
• Configuration decisions that lack context or a clear audit trail

The result? Chaos. Making configuration changes in such an environment can be daunting. So, how do we bring order to this chaos?

How Infrastructure as Code Brings Control

Infrastructure as Code (IaC) is instrumental in smoothing out the rough edges of legacy takeovers. IaC involves managing infrastructure changes as declarative files, checked into version control, and subjected to the same quality checks as application code. While not strictly required, IaC often includes automating the application of these changes, ensuring consistency and reducing errors.

In the context of legacy system takeovers, IaC helps by:

• Bringing clarity: Every piece of existing configuration is brought into the codebase and managed by IaC tools, helping the team understand the full infrastructure and spot inconsistencies.
• Managing dependencies: IaC automatically handles dependencies between configurations, reducing the risk of missed downstream changes and forcing the team to explicitly define resource relationships.
• Highlighting technical debt: IaC reveals infrastructure design issues that hinder maintainability, offering a holistic view of the cloud architecture.
• Enabling automation: Automation reduces the risk of human error during deployments, making the process more reliable and repeatable.

Effective Takeovers

When adopting IaC in a legacy cloud environment, our team follows a step-by-step approach:

1. Choose the Right Tooling: We prefer Pulumi, but Terraform or CDK are also solid choices. The key is to pick a tool that aligns with your team’s existing skillset and comfort level.
2. Define Environment Boundaries: Before managing resources, decide how to group them into easily replicable environments or stacks. This typically includes staging, production, development, and a “base” environment for shared resources. Identify and document dependencies, ensuring each application environment relies only on the base environment.
3. Incremental Import Based on Risk: Most IaC tools allow you to import existing resources into their managed state via CLI commands. Start with low-risk resources, such as those in development or staging environments, along with base resources. As you import, diligently identify and codify relationships between resources.
4. Automate Changes for One Environment: Once all resources for a given environment are managed by your IaC tooling, automate their application through your preferred CI/CD pipeline. This approach ties configuration changes to the version control lifecycle, ensuring auditability and reducing the risk of human error.
5. Resolve Environment Inconsistencies: You’ll likely uncover configuration inconsistencies between environments. These discrepancies can lead to downstream failures, like a production deployment breaking despite working fine in staging. Take this time to refactor the architecture for greater parity before automating high-risk environments like production.
6. Complete the Import and Automation: Keep production deployments manual at first to build confidence in the completeness and maintainability of your configurations. Gradually transition to automated deployments for all environments, adding appropriate human gates in the CD process based on your risk tolerance.

This process can be lengthy and challenging, depending on the complexity of the software. However, by adopting IaC incrementally, you break the task into manageable chunks. The result is a system that your infrastructure team understands, is well-documented through code, and automated, freeing up time for higher-value work.

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Adopting Infrastructure as Code (IaC) when taking over legacy cloud systems can turn chaos into a predictable, manageable, and scalable environment. While the process can be challenging, the benefits—enhanced documentation, automated deployments, and reduced risk of human error—make it well worth the effort. By systematically implementing IaC, your team can take control of even the most complex legacy infrastructures, ensuring stability and ease of future growth.

If you’re ready to streamline your cloud operations and embrace the power of IaC, check out our MM offering and reach out to us today.