Declarative vs Programmatic Infrastructure as Code

What is the difference between declarative and programmatic Infrastructure as Code? Why it matters and when you should use each? Best practices for writing good Infrastructure as Code when using AWS CloudFormation, AWS SAM, AWS CDK, Pulumi, Terraform, SST, Serverless Framework, etc.

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1. SLOVAKIA March 26, 2025

2. Declarative vs Programmatic
 Infrastructure as Code Jakub Gaj Senior Cloud Architect
3. Prototyping new cloud solutions Interactive demos for non-developers My name is Jakub and I 🧡 ClickOps 😎 Jakub Gaj AWS Community Builder AWS New Voices Speaker Experimenting with cloud services Hot fixes in pre-production accounts
4. “Infrastructure as Code is the practice of provisioning and managing infrastructure using code, as opposed to doing it interactively 
 or with non-code automation tools.” Kief Morris Infrastructure as Code, 2nd Edition
 (O’Reilly Media) ‣ Fundamental differences ‣ Optimal use cases ‣ Framework considerations ‣ Best practices Declarative & programmatic approach:
5. Evolution of IT infrastructure Iron Age Virtual Age Bare Metal in Data Centers Virtualization of Compute, Storage, Networking Cloud Providers / Services AI Services Cloud Era AI Era
6. Milestones of Everything as Code ‣ Bash Shell (BSH) ‣ Korn Shell (KSH) ‣ Distributed Shell (DSH) ‣ Batch ‣ PowerShell ‣ Perl ‣ Python Shell Scripting ‣ CFEngine ‣ Puppet ‣ Chef ‣ Ansible ‣ Salt (SaltStack)
 
 Configuration as Code ‣ AWS CloudFormation ‣ HashiCorp Terraform ‣ Microsoft Azure
 Resource Manager ‣ Microsoft Bicep ‣ Google Cloud
 Deployment Manager
 Infrastructure as Code
7. Milestones of Everything as Code ‣ Docker ‣ Kubernetes ‣ AWS Serverless
 Application Model ‣ Serverless Framework
 
 
 Containers & FaaS ‣ AWS CDK ‣ CDK for Terraform ‣ Pulumi Engine ‣ SST Framework
 
 
 Cloud Development Kits ‣ AWS CodeWhisperer ‣ AWS Q Developer ‣ Pulumi Copilot ‣ GitHub Copilot ‣ Anthropic Claude Code ‣ Cursor
 
 AI-Assisted Development
8. Core aspects of declarative IaC Domain-specific languages
 (CF, HCL, Bicep) Limited built-in
 logic capabilities Code readability
 (WYSIWYG) Can become lengthy for complex infra Focus on infra layer 
 (shared platforms) Better suited for low-level resources definition
9. Popular declarative frameworks AWS
 CloudFormation AWS Serverless Application Model Serverless Framework HashiCorp Terraform CE Linux Foundation OpenTofu Microsoft 
 Bicep (ARM) Google Cloud Deployment Manager AWS Amplify
10. Core aspects of programmatic IaC Standard programming languages
 (Python, TypeScript) Advanced logic:
 conditional statements, loops, etc Custom abstractions:
 patterns, constructs, packages Integrations with existing development workflows Focus on app layer (business logic) Better suited for high-level app-centric deployments
11. Popular programmatic frameworks Pulumi Engine SST Framework CDK for Terraform AWS Cloud Development Kit
12. State management: backend & locking AWS CloudFormation Pulumi Engine Google DM Microsoft ARM Terraform Terraform
 Cloud / HCP Terraform
 Enterprise Pulumi Cloud Spacelift Remote Storage Cloud Service Enterprise IaC Platforms
13. Demo time! SST Framework AWS Cloud Development Kit AWS Cloud Development Kit Power of
 Constructs Deploy Astro site with SST Migrate your
 CF stacks AWS Cloud Development Kit Conditional
 resources
14. Some best practices Infrastructure, Configuration, Security Policies, Documentation, Diagrams Test Driven Development, Unit / Integration Tests (Automated Test Suites) Group components into deployable stacks, separate stateful / stateless resources Define everything as code (apply SDLC processes) Continuously test and deliver all work in progress Build small pieces that can be changed independently
15. Key takeaways Define lifecycle policies to protect resources from being accidentally deleted Resource Protection Use IaC linters & security scanners to enforce best practices Static Code Analysis Use CDK Constructs, Terraform Modules, Pulumi Packages, etc Reusable Patterns Use CI/CD pipelines to deliver any changes to infrastructure Continuous Deployments Implement regular drift detection checks and remediation actions Drift Detection Implement automated rollback mechanisms for failed deployments Automated Rollbacks
16. 🇬🇧 Thank you! 🇵🇱 Dziękuję! 🇸🇰 Ďakujem! 🇨🇿 Děkuju! Let’s connect! Social Profiles Tech Blogs GitHub Repos Resources / Slides Jakub Gaj