Trunk-Based Development and CI/CD Pipelines

The Problem with Long-Lived Feature and Release Branches

Traditional branching strategies have served development teams for decades, but as software systems grow in complexity and team sizes scale, the limitations of long-lived feature and release branches become increasingly problematic. Understanding these challenges is the first step toward adopting more effective development practices.

The Hidden Costs of Long-Lived Branches

Exponential Merge Conflicts

Long-lived feature branches increase merge conflicts exponentially as codebases and teams grow. The longer a branch exists, the more the mainline diverges, creating a compounding integration challenge that consumes valuable engineering time.

Environment Branch Complexity

Environment and release branches add complexity, causing delays in integration and deployment. Managing multiple branch hierarchies requires coordination overhead that scales poorly with team growth.

Integration Hell

Developers face “integration hell” where merging becomes time-consuming, error-prone, and blocks delivery. What should be a routine process becomes a dreaded event requiring dedicated time and mental energy.

Consider the Gitflow branching model as a concrete example. While popular, Gitflow’s multiple primary branches (develop, release, and hotfix) require complex coordination between teams. A typical scenario involves developers working on feature branches for weeks, periodically syncing with develop, then going through a separate release branch stabilization phase. This multi-stage process introduces delays at each transition point and creates opportunities for bugs to hide in branch-specific code paths.

The cumulative effect of these costs manifests as reduced team velocity, increased bug rates in production, and developer frustration. Engineering teams spend more time managing branches than delivering features, and the time from code completion to production deployment stretches from hours to weeks.

Why Long-Lived Branches Hurt CI/CD

Pipeline Ineffectiveness

CI/CD pipelines lose effectiveness when branches diverge for days or weeks. The fundamental promise of continuous integration, that code is always in a deployable state, breaks down when integration happens infrequently. Automated tests run late or on stale code, increasing risk of broken builds in mainline.

Delayed Feedback Loops

Delayed integration leads to large, risky merges that break the build and slow feedback loops. When developers finally merge their feature branch, they discover conflicts and issues that could have been caught days earlier with more frequent integration. The cost of fixing these issues compounds with time.

Release Bottlenecks

Teams often postpone releases waiting for branch stabilization, defeating continuous delivery goals. The promise of deploying at any time becomes theoretical rather than practical. Release planning becomes a complex exercise in branch management rather than a simple decision about which features to enable.

The technical debt incurred by long-lived branches extends beyond immediate merge conflicts. Test coverage becomes less meaningful when tests run against code that hasn’t been integrated with the latest mainline changes. This creates a false sense of security. Passing tests on a feature branch don’t guarantee those same tests will pass after merging. The result is a brittle CI/CD pipeline that catches issues too late in the development cycle, when they’re most expensive to fix.

Why Environment-Specific Branches Are Problematic

Environment-specific branches (e.g., release, staging, production) create significant friction and hidden costs, hindering agility and increasing deployment risk. This approach makes continuous delivery aspirational rather than practical.

These challenges cumulatively reduce deployment frequency, increase lead time for changes, and erode trust in the delivery process. Adopting a single source of truth, typically a trunk-based approach, is crucial for overcoming these hurdles and enabling true continuous delivery.

What is Trunk-Based Development?

Trunk-based development represents a paradigm shift in how teams approach version control and integration. Rather than isolating work in long-lived branches, TBD emphasizes frequent integration into a single shared branch, fundamentally changing how teams collaborate and deliver software.

This approach isn’t merely a technical practice. It’s a philosophy that prioritizes continuous integration, rapid feedback, and maintaining always-deployable code. By understanding the core principles and benefits of trunk-based development, teams can transform their delivery capabilities and achieve true continuous deployment.

Core Principles of Trunk-Based Development (TBD)

Single Shared Trunk

Developers commit small, frequent changes directly to a single shared branch called the “trunk”, “main”, or “master”. This becomes the source of truth for the entire codebase, eliminating confusion about which branch represents current state.

Short-Lived Branches

Feature branches, if used, are extremely short-lived (measured in hours to a day maximum) and merged quickly. Never getting more than a few commits behind the trunk before being merged back in. The goal is to minimize divergence while still allowing for code review and CI validation before integration.

Always Deployable

The trunk is always kept in a deployable, stable state, often referred to as keeping the build “green.” This requires discipline and robust automated testing but enables deployment at any moment without special preparation.

Feature Flag Decoupling

Feature flags enable incomplete features to be merged safely without impacting production behavior. This decouples deployment from release, allowing code to flow continuously while controlling feature visibility independently. See the VergeOps whitepaper on feature flags for more information.

These principles work together synergistically. Short integration cycles reduce merge conflicts while feature flags provide safety. Maintaining a green trunk creates confidence while frequent commits provide rapid feedback. The result is a development workflow that naturally supports continuous integration and deployment rather than fighting against it.

Importantly, trunk-based development scales effectively across team sizes. Small teams might commit directly to trunk with post-commit review, while larger teams might use short-lived pull request branches that merge within hours. The key is that all code integrates frequently into the shared trunk, regardless of the specific mechanics.

How Trunk-Based Development Simplifies Development

Natural Continuous Integration

Continuous integration becomes natural when code is integrated multiple times daily. Instead of being a special event, integration happens as part of normal development rhythm, making the process routine and low-risk.

Minimized Conflicts

Merge conflicts are minimized due to frequent, small merges. When changes integrate quickly, the surface area for conflicts remains small and manageable, reducing the cognitive load on developers.

Faster Reviews

Code reviews are faster and more focused on incremental changes. Reviewers can provide meaningful feedback on small, cohesive changes rather than being overwhelmed by large feature dumps.

The simplification extends to release management as well. Without long-lived release branches, teams can enable rapid, reliable releases that support continuous delivery pipelines. Every commit to trunk is a potential release candidate, and the decision to deploy becomes a business decision rather than a technical coordination challenge.

Developer experience improves significantly under trunk-based development. Engineers spend less time dealing with merge conflicts and branch management, and more time writing code and solving business problems. The reduced cognitive overhead of managing multiple branch states allows developers to maintain better focus and context, ultimately improving both productivity and code quality.

Key Insight: TBD shifts the challenge from managing branches to maintaining quality through automation. The investment in testing and feature flags pays dividends in reduced integration friction.

Integrating CI/CD with Trunk-Based Development

Trunk-based development and CI/CD are symbiotic practices. Each amplifies the value of the other. While TBD provides the branching strategy that enables continuous integration, a well-architected CI/CD pipeline provides the automation and safety nets that make trunk-based development practical and sustainable.

CI/CD Pipeline Stages in TBD

Source

Developers push small commits to trunk or short-lived branches. Version control triggers the pipeline automatically, initiating the validation process within seconds of code commit.

Build

Automated builds triggered immediately to verify integration. Compilation, dependency resolution, and artifact creation happen in a clean environment, ensuring reproducibility.

Test

Comprehensive automated test suites run covering unit, integration, and functional tests. Test results provide fast feedback about code quality and integration issues.

Deploy

Successful builds are deployed automatically or on-demand to chosen environments. Deployment automation removes manual steps and human error from the release process.

Each pipeline stage serves as a quality gate, with failures preventing progression to subsequent stages. This fail-fast approach ensures issues are caught early when they’re cheapest to fix. The pipeline architecture should be designed for speed. Every minute of pipeline runtime is a minute developers wait for feedback, so optimization is critical.

Modern CI/CD platforms provide sophisticated capabilities beyond these basic stages: parallel execution, deployment strategies like blue-green or canary deployments, and integration with monitoring and observability tools. Leveraging these capabilities allows teams to build confidence in their deployments while maintaining rapid release cadence.

Best Practices for CI/CD in TBD

Metrics to Track

• Pipeline success rate (target: >95%)
• Mean time to recovery from broken builds
• Pipeline execution time (target: <10min)
• Deployment frequency (daily or higher)
• Lead time from commit to production

Tagging Release Candidates

In Trunk-Based Development, where the main branch is always considered shippable, the practice of tagging release candidates is paramount. This process formalizes the identification of deployable code versions directly from the trunk. Once a commit successfully navigates through all CI/CD pipeline stages and is deemed stable and ready for release, the pipeline automatically applies a specific tag to that commit.

These tags, often following semantic versioning (e.g., v1.2.3) or a date-based format (e.g., release-20231027-1), serve as immutable pointers to a precise state of the codebase. This creates a definitive record of what was released, providing a robust mechanism for managing software versions in a continuous delivery environment.

This best practice reinforces the “always shippable” nature of the trunk by providing a robust, automated way to mark stable versions. It enables teams to confidently deploy, roll back, or re-release any past version with minimal friction, supporting a truly agile and responsive delivery model.

Single Artifact Promotion: The “Build Once, Promote Everywhere” Principle

In the world of Trunk-Based Development and CI/CD, a foundational best practice is the “build once, promote everywhere” principle. This strategy dictates that a software artifact, such as a Docker image, JAR file, or executable, should be built only a single time at the earliest stage of the CI/CD pipeline. This immutable artifact is then the exact same component that is deployed and promoted through all subsequent environments (development, staging, user acceptance testing, and ultimately production) without any modifications or rebuilds along the way.

This practice contrasts sharply with the anti-pattern of rebuilding artifacts for each environment, where slight variations in build tools, dependencies, or configuration parameters can inadvertently introduce subtle, hard-to-diagnose bugs. By committing to “build once, promote everywhere,” teams significantly reduce the risk of environment-specific failures, accelerate release cycles, and foster a more stable and predictable deployment process that is essential for continuous delivery.

More Best Practices

Beyond these core practices, establish clear team agreements about commit frequency, code review SLAs, and incident response procedures. Document your branching strategy and CI/CD processes so new team members can onboard quickly. Create runbooks for common scenarios like fixing a broken build or rolling back a deployment.

Cultural factors matter as much as technical practices. Foster a blameless culture where breaking the build is treated as a learning opportunity rather than a failure. Celebrate quick fixes and recognize developers who maintain high commit frequency. Make trunk health visible and shared responsibility across the entire team.

Common Pitfalls to Avoid

Warning: The most dangerous pitfall is partial adoption. Half-hearted trunk-based development, keeping some long-lived branches while attempting TBD, creates the worst of both worlds: complexity without benefits.

Many teams fail with TBD not due to technical issues but because they don’t address the organizational and cultural prerequisites. Executive support, dedicated time for infrastructure work, and patience during the transition period are all critical success factors that go beyond the technical mechanics.

Tips and Tricks for Success

Advanced teams can explore sophisticated techniques like synthetic monitoring to validate deployments, chaos engineering to test system resilience, and progressive delivery strategies that combine feature flags with canary deployments for maximum safety. The key is to build confidence through layers of automation rather than relying on manual verification processes that don’t scale.