Understanding Trunk-Based Development for High-Performance Teams

What is Trunk-Based Development?

Trunk-Based Development (TBD) is a source control methodology where developers collaborate on code in a single branch called the "trunk," resisting the temptation to create long-lived feature branches. In modern Git workflows, this trunk is typically the main or master branch.

Why "Trunk"?

The name originates from the visual metaphor of a tree's structure in version control systems:

• Trunk: The main line of development (hence main branch)
• Branches: Divergent paths that extend from the trunk
• Merge: When branches are reintegrated back into the trunk

The terminology dates back to older version control systems like SVN and CVS, where this tree-like visualization was more prominent. The "trunk" represents the central, authoritative source of truth for your codebase, with all development efforts either happening directly on it or quickly flowing back into it.

In Trunk-Based Development, the trunk remains the primary integration point, with minimal branching and rapid, frequent merges. This contrasts with workflows like GitFlow, where multiple long-lived branches (develop, release, feature) exist simultaneously.

Why Trunk-Based Development?

Performance Metrics That Matter

The data speaks for itself: The DORA State of DevOps research consistently shows that high-performing teams use trunk-based development. Teams practicing TBD achieve:

• 24x more frequent deployments
• 2.5x less time for changes to reach production
• 3x lower change failure rate
• 5x faster recovery from incidents

The Technical Benefits

1. Reduced Merge Complexity: Small, frequent commits minimize merge conflicts that plague long-lived feature branches
2. Continuous Integration in Practice: When everyone commits to main, you're actually practicing CI, not just running a CI server
3. Acceleration of Feedback Loops: Code gets reviewed, tested, and deployed faster, catching issues early
4. Simplified Git Workflows: Complex branching strategies create cognitive overhead and process friction

How to Implement Trunk-Based Development

Core Principles

Trunk-based development revolves around three key practices:

1. Direct commits to trunk (main) for small changes
2. Short-lived feature branches (less than 1-2 days)
3. Continuous integration running against trunk

Transitioning Your Team

1. Start With Feature Flags

Feature flags are your safety net when transitioning to trunk-based development:

def checkout_process(user):
    if feature_flags.is_enabled('new_checkout_flow', user.id):
        return new_checkout_process(user)
    else:
        return legacy_checkout_process(user)

This lets you:

• Merge incomplete features safely into trunk
• Control feature exposure with gradual rollouts
• A/B test new functionality
• Quickly disable problematic features without rolling back

2. Master Small, Atomic Commits

Break down large features into small, independently valuable changes:

# Bad approach - one massive commit
git add .
git commit -m "Implement user notifications feature"

# Good approach - series of focused commits
git add src/models/notification.ts
git commit -m "Add notification data model"

git add src/services/notification-service.ts
git commit -m "Implement notification delivery service"

git add src/components/NotificationBadge.tsx
git commit -m "Add UI component for notification badge"

3. Implement Pre-Merge Verification

Strong automated testing is essential:

# Example GitHub Actions workflow
name: Trunk Verification

on:
  push:
    branches: [ main ]
  pull_request:
    branches: [ main ]

jobs:
  verify:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - name: Set up environment
        run: make setup
      - name: Lint
        run: make lint
      - name: Unit tests
        run: make test
      - name: Integration tests
        run: make integration-test

4. Optimize Pull Requests

For small feature branches:

• Limit PR scope to 200-400 lines of code
• Define clear completion criteria
• Automate code style and quality checks
• Establish SLAs for PR reviews (<4 hours)

5. Create a Release Strategy

Decouple deployment from release using one of these approaches:

1. Deploy-but-hide: Code is deployed but hidden behind feature flags
2. Dark launches: New code paths execute in parallel but don't affect users
3. Canary releases: Gradually expose new functionality to increasing user segments

Common Challenges and Solutions

"How do we handle long-running features?"

Solution: Break them into incremental, independently valuable changes that can be merged separately. Use feature flags to hide incomplete work.

"What about experimental work?"

Solution: For exploratory code, create a short-lived branch and either:

• Integrate promising experiments quickly to trunk (behind flags)
• Discard failed experiments entirely

"How do we manage releases?"

Solution: Separate deployment from release with these patterns:

• Continuous deployment to staging environments
• Feature flags for production control
• Semantic versioning with git tags

Getting Started Today

1. Audit your current workflow - Measure time from commit to deployment
2. Implement feature flagging - Choose a library or build minimal implementation
3. Train your team - Focus on writing small, independent changes
4. Improve test automation - Prioritize fast, reliable tests
5. Gradually decrease branch lifetimes - Aim for <1 day branch lifespans

Trunk-based development isn't just a different branching strategy—it's a fundamental shift in how teams collaborate and deliver software. By focusing on small changes, incremental value, and robust automation, you'll build a development workflow that scales with your team and accelerates your delivery cadence.

The most successful development teams have already made this transition. The question isn't whether you should adopt trunk-based development, but how quickly you can implement it to start seeing the benefits.