How do you integrate code continuously while keeping incomplete features hidden from users? This is the classic dilemma facing teams that want to move fast without compromising quality. The answer lies in combining two powerful practices: trunk-based development and feature flags.
Why Long-Lived Feature Branches Kill Continuous Integration
Most development teams use feature branches: one branch per feature, merged when development is complete. In theory, it's clean. In practice, it creates serious problems.
Merge Conflicts Multiply Over Time
The longer a branch lives, the more it diverges from the main branch. What starts as a simple feature becomes a merge nightmare with dozens of conflicts to resolve manually.
Late Integration Means Late Bug Discovery
You only discover that your code breaks a colleague's work at merge time—sometimes weeks after writing the code. By then, context is lost and fixes are expensive.
Big Bang Deployments Increase Risk
Merging a large branch means deploying many changes at once. The more code you ship simultaneously, the higher the probability of production incidents.
Long-lived feature branches contradict the core principle of continuous integration: integrate code frequently to detect problems early.
How Feature Flags Enable Trunk-Based Development
Trunk-based development takes a radically different approach: everyone commits directly to the main branch (trunk/main), with frequent commits and very short-lived branches (a few hours maximum).
But how do you avoid deploying unfinished code to production? This is where feature flags become essential.
The Concept: Deploy Dark, Release When Ready
Your code is merged and deployed, but it remains "dark"—hidden behind a disabled flag. Users see nothing until you explicitly activate the flag.
This approach gives you the best of both worlds:
- True continuous integration: Your code integrates daily into the main branch
- Release control: You decide exactly when users see the new feature
- Instant rollback: Problem detected? Disable the flag—no revert needed
Trunk-Based Development Workflow with Feature Flags
Here's how high-performing teams combine trunk-based development with feature flags:
Step 1: Create the Feature Flag First
Before writing any code, create your feature flag in Flagster. It starts disabled by default.
Step 2: Develop Behind the Flag
1// New code is protected by the feature flag2if (flagster.isEnabled("new-checkout-flow")) {3 return <NewCheckoutPage />;4}5return <CurrentCheckoutPage />;
Step 3: Commit and Deploy Daily
Every day, push your changes to main. The code deploys to production, but users don't see it because the flag is disabled. Your CI/CD pipeline runs normally.
Step 4: Activate with Progressive Rollout
Once development is complete and tested, enable the flag progressively: internal team first, then 10% of users, then everyone.
Key Benefits for DevOps Teams
Combining trunk-based development with feature flags delivers measurable improvements:
- 90% fewer merge conflicts: Branches live hours, not weeks
- Earlier bug detection: Code integrates and tests run daily
- Lower deployment risk: Small, frequent changes instead of big releases
- Decoupled deploy and release: Marketing can schedule launches independently
- Better team collaboration: Everyone works on the same codebase
Feature flags transform continuous deployment from a source of stress into a competitive advantage.
Getting Started with Feature Flags for CI/CD
Feature flags aren't just a progressive rollout tool. They're essential DevOps enablers that let you adopt modern practices like trunk-based development without sacrificing control over what users see.
Ready to modernize your development workflow? Try Flagster for free and discover how feature flags can transform your continuous integration pipeline.
