GitOps: Monorepo vs Polyrepo - A Practical Comparison

Introduction

When implementing GitOps for infrastructure and application deployments, one of the first decisions teams face is whether to use a monorepo (single repository) or polyrepo (multiple repositories) approach. Both strategies have been successfully implemented at scale, and the choice depends on your team structure, organization size, and specific requirements.

This guide provides a clear comparison of both approaches to help you make an informed decision.

What is Monorepo?

A monorepo is a single repository that contains all your code, configurations, and manifests in one place.

Structure Example:

platform-repo/
├── applications/
│   ├── app-a/
│   ├── app-b/
│   └── app-c/
├── infrastructure/
│   ├── terraform/
│   └── kubernetes/
├── helm-charts/
└── shared-libraries/

What is Polyrepo?

A polyrepo approach uses multiple separate repositories, typically organized by service, application, or team.

Structure Example:

app-a-repo/
├── src/
└── k8s/

app-b-repo/
├── src/
└── k8s/

infrastructure-repo/
├── terraform/
└── kubernetes/

helm-charts-repo/
└── charts/

Monorepo: Advantages

1. Atomic Changes Across Multiple Services

• Make coordinated changes across multiple services in a single commit
• Update shared libraries and dependent services together
• No version synchronization issues between repositories

2. Simplified Dependency Management

• All dependencies visible in one place
• No need to track versions across multiple repositories
• Easier to ensure consistency across projects

3. Single Source of Truth

• Everything in one location
• Easier to search across entire codebase
• Unified documentation and standards

4. Easier Code Sharing

• Shared libraries and utilities in same repo
• No need to publish internal packages
• Immediate access to shared code changes

5. Consistent Tooling and CI/CD

• One set of CI/CD configurations
• Unified linting, testing, and deployment standards
• Single place to update tooling

6. Simplified Code Review Process

• Cross-service changes in single pull request
• Reviewers can see full context of changes
• No need to coordinate multiple PRs across repos

Monorepo: Disadvantages

1. Large Repository Size

• Clone times can become significant (multi-GB repositories)
• Git operations slow down with repository growth
• Requires Git LFS or partial clone strategies for large repos

2. Complex CI/CD Pipelines

• Need intelligent path-based triggers
• Must avoid running all tests for every change
• Requires sophisticated build tools (Bazel, Nx, Turborepo)
• CI/CD can become slow without proper optimization

3. Permission Management Complexity

• Difficult to restrict access to specific parts of codebase
• CODEOWNERS files can become complex
• Everyone has visibility into all code
• Not suitable for strict access control requirements

4. All-or-Nothing Access

• Contractors and external contributors see entire codebase
• Hard to grant limited access to specific services
• Compliance challenges when different services have different security requirements

5. Potential for Widespread Breaking Changes

• One bad commit can affect multiple services
• Higher blast radius for mistakes
• Requires discipline and strong testing

6. Learning Curve for New Developers

• New developers must understand entire repository structure
• Can be overwhelming with many services
• Longer onboarding time

Polyrepo: Advantages

1. Clear Ownership Boundaries

• Each repository has clear team ownership
• Easy to assign permissions per repository
• Natural organizational structure

2. Independent Release Cycles

• Teams can deploy at their own pace
• No coordination needed for releases
• Faster iteration for individual services

3. Smaller Repository Size

• Fast clone and checkout times
• Git operations remain fast
• Easier to work with individual repos

4. Simpler CI/CD Per Repository

• Each repo has focused CI/CD pipeline
• Faster build and test times per repo
• Easy to understand and maintain

5. Granular Access Control

• Fine-grained permissions per repository
• Easy to manage contractor access
• Better compliance separation

6. Technology Diversity

• Different repos can use different tech stacks
• Each service can have appropriate tooling
• No need for unified build system

7. Isolated Failures

• Issues in one repository don't affect others
• Reduced blast radius for problems
• Better fault isolation

Polyrepo: Disadvantages

1. Cross-Repository Changes Are Painful

• Updates spanning multiple services require multiple PRs
• Must coordinate merging and deployment order
• Time-consuming for coordinated features

2. Dependency Version Hell

• Hard to track which services use which library versions
• Version drift across repositories
• Security updates require changes across many repos

3. Code Duplication

• Shared code often duplicated across repositories
• Utility functions and helpers copied
• Inconsistent implementations

4. Multiple Sources of Truth

• Configuration scattered across repositories
• Hard to get complete picture of system
• Documentation fragmented

5. Complex Tooling Requirements

• Need repository management tools
• Automation for cross-repo operations
• Additional tooling overhead

6. Difficult to Enforce Standards

• Each repository may drift in standards
• CI/CD configurations can diverge
• Requires repository templates and enforcement

7. Visibility Challenges

• Hard to search across all code
• Dependency graphs difficult to maintain
• Impact analysis for changes is complex

GitOps Implementation Considerations

Monorepo with ArgoCD/FluxCD

Approach:

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: platform
spec:
  source:
    repoURL: https://github.com/company/platform
    path: kubernetes/
    targetRevision: main

Advantages:

• Single ArgoCD Application for all services
• Atomic deployments across multiple services
• Simple sync operations
• Easy to see all manifests

Disadvantages:

• All services sync together
• One repository issue blocks all deployments
• Harder to have different sync policies per service
• Large repository can slow down sync operations

Polyrepo with ArgoCD/FluxCD

Approach:

# Separate Application per service
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: app-a
spec:
  source:
    repoURL: https://github.com/company/app-a
    path: k8s/
---
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: app-b
spec:
  source:
    repoURL: https://github.com/company/app-b
    path: k8s/

Advantages:

• Independent sync policies per service
• Isolated failures
• Team autonomy
• Different repositories can sync at different rates

Disadvantages:

• Many ArgoCD Applications to manage
• Coordinated deployments require manual orchestration
• Need to track dependencies manually
• ArgoCD UI can become cluttered

Hybrid Approach (App-of-Apps Pattern)

Many organizations use a hybrid approach:

Structure:

infrastructure-monorepo/
├── argocd/
│   ├── apps/           # Defines all applications
│   └── infrastructure/ # Platform services
├── terraform/
└── base-manifests/

app-a-polyrepo/
├── src/
└── k8s/

app-b-polyrepo/
├── src/
└── k8s/

Benefits:

• Infrastructure and platform as monorepo (atomic updates)
• Applications as polyrepos (team autonomy)
• ArgoCD App-of-Apps manages both
• Balance between control and flexibility

Decision Matrix

When to Choose Monorepo

Best for:

• Small to medium teams (<50 developers)
• Tightly coupled services that change together
• Platform teams managing infrastructure
• Organizations prioritizing consistency
• Teams with strong CI/CD expertise
• When atomic changes across services are common

Example Use Cases:

• Platform infrastructure (Kubernetes + Terraform + Helm)
• Microservices that share significant code
• Startups with small engineering teams
• Internal tools and services

When to Choose Polyrepo

Best for:

• Large organizations (>100 developers)
• Independent teams with clear boundaries
• Services with different release schedules
• Strict access control requirements
• Compliance-driven environments
• Acquired companies or legacy systems

Example Use Cases:

• Large microservices architectures
• Multi-team organizations
• Services with different compliance requirements
• Open source projects
• Client projects with separate repositories

When to Choose Hybrid

Best for:

• Most medium to large organizations
• Mixed requirements for control and autonomy
• Platform team managing infrastructure + app teams
• Organizations transitioning from one model to another
• When you want infrastructure consistency but application autonomy

Example Use Cases:

• Infrastructure as monorepo + applications as polyrepos
• Core platform as monorepo + customer-facing services as polyrepos
• Shared components as monorepo + team services as polyrepos

Essential Tooling

For Monorepo Success

Build Optimization:

• Bazel - Google's build system for large monorepos
• Nx - Build system for JavaScript/TypeScript
• Turborepo - Fast builds with intelligent caching
• Pants - Build orchestration for Python

Git Optimization:

• Partial clones (git clone --filter=blob:none)
• Sparse checkout for working on specific areas
• Git LFS for large binary files

CI/CD:

• Path-based triggering (only run tests for changed code)
• Distributed caching
• Parallel test execution

For Polyrepo Success

Repository Management:

• Renovate/Dependabot - Automated dependency updates
• Repository templates - Consistency across repos
• Meta - Manage multiple repositories as one

Automation:

• Scripts for cross-repo operations
• Automated repository creation and setup
• Centralized CI/CD configuration management

Visibility:

• Service catalog
• Dependency tracking tools
• Cross-repository search tools

Migration Considerations

Moving from Polyrepo to Monorepo

Challenges:

• Preserving Git history
• Resolving file path conflicts
• Rewriting CI/CD pipelines
• Updating import paths and dependencies
• Training team on new structure

Time Investment: 3-9 months depending on scale

Moving from Monorepo to Polyrepo

Challenges:

• Splitting repositories while preserving history
• Extracting shared code into libraries
• Creating separate CI/CD for each repo
• Managing new dependencies
• Coordinating cross-repository changes

Time Investment: 6-12 months depending on scale

Important: Migration is expensive and disruptive. Choose carefully at the start.

Best Practices

For Monorepo

1. Implement strong CI/CD with path-based triggers
2. Use CODEOWNERS for code ownership
3. Set up pre-commit hooks for consistency
4. Invest in build optimization tools
5. Document repository structure clearly
6. Use branch protection and required reviews
7. Monitor repository size and performance

For Polyrepo

1. Create and maintain repository templates
2. Automate dependency updates
3. Maintain a service catalog
4. Document inter-repository dependencies
5. Use consistent naming conventions
6. Implement automated repository setup
7. Track versions and dependencies centrally

For Hybrid

1. Clearly define what goes in monorepo vs polyrepo
2. Document the decision criteria
3. Use ArgoCD App-of-Apps pattern
4. Maintain consistent practices across both
5. Clear ownership boundaries

Conclusion

There is no universally "correct" choice between monorepo and polyrepo. Both approaches work successfully at scale when implemented properly.

Key Takeaways:

• Monorepo excels at consistency and atomic changes but requires tooling investment
• Polyrepo provides autonomy and isolation but adds coordination overhead
• Hybrid approaches offer a practical middle ground for many organizations
• Organization structure matters more than technical preferences
• Tooling investment is critical for either approach to succeed
• Migration between approaches is expensive and time-consuming

Choose based on your team size, organizational structure, service coupling, and access control requirements. Start with the simplest approach that meets your needs, and be prepared to evolve as your organization grows.

The right repository strategy is the one that enables your team to move quickly while maintaining quality and security.

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