Why Your Code Review Process Might Be Broken: The Case for Trunk-Based Development
If you work on a software team, you likely spend a good chunk of your week waiting. Waiting for builds, waiting for approvals, and waiting to resolve the inevitable merge conflicts that happen when a large change has been pending for too long.
Traditionally, many teams rely on feature branching, where a developer creates a branch from the main trunk and works in isolation for days or weeks before enduring a complex merge event. However, this approach often leads to massive bottlenecks, procrastination, and deployment risks.
The solution? Trunk-Based Development (TBD), a practice where developers divide their work into small batches and merge them into the trunk at least once a day.
Here is a look at why your current workflow might be failing, and how trunk-based development can fix it.
The Symptoms of a Broken Git Workflow
When teams rely heavily on long-lived feature branches, several painful process issues usually emerge:
- Review Bottlenecks and Procrastination: An overly heavy, asynchronous code review process causes reviewers to procrastinate because large code reviews are highly complex. As a result, pull requests sit idle for weeks, constantly accumulating merge conflicts as the main codebase moves on.
- The "Code Freeze" Reality: Because large merges frequently introduce bugs or regressions, teams are forced to rely on "code lock" or stabilization periods to ensure the software actually works.
- Ineffective Reviews: When changes finally get reviewed, they are often too large for anyone to reason about effectively. Defects easily slip past reviewers, diminishing the value of the review process entirely.
Enter Trunk-Based Development and Small Batches
Trunk-based development addresses these governance holes by enforcing a simple rule: everyone integrates small, tested changes into one shared trunk frequently. This eliminates long integration phases and reduces the complexity of merge events.
Here is how successful teams make the shift:
1. Develop in Small Batches
Working in small batches is the cornerstone of TBD. Instead of massive feature branches, developers should aim to break work down into independent, testable increments that can be completed in hours rather than weeks.
This is especially critical today with the rise of generative AI. While AI coding assistants excel at generating large blocks of code rapidly, these massive machine-generated changes are incredibly difficult to review and integrate safely. Enforcing small batches acts as a critical safety net for AI adoption, shifting the focus from raw code generation to thoughtful verification and preventing AI velocity from turning into software instability.
2. Dark Launching and Feature Toggles
How do you merge code daily if the feature isn't finished? The answer is dark launching and feature toggles. By starting development at the API layer or hiding incomplete UI elements behind conditional configuration settings, you can merge small slices of code into the trunk without exposing half-finished features to your users. This prevents giant feature branches from rotting in isolation while waiting for a single massive release.
3. Synchronous Reviews
Instead of submitting a pull request and moving on to another task while waiting days for feedback, teams should prioritize synchronous code reviews. When a developer is ready to commit, they should ask a peer to review the code right then, or utilize pair programming. This prevents merge delays and stops the downward spiral of complex, delayed reviews.
4. Continuous Integration (The Trunk is Always Green)
TBD goes hand-in-hand with Continuous Integration (CI). Automated tests must run on every commit to ensure the trunk is kept in a working state. Developers are responsible for keeping the build process green; if a change breaks the CI process, the team must either fix it immediately or revert the change.
The Important detail
Moving to Trunk-Based Development requires discipline and a shift in how developers think about breaking down work. However, by abandoning long-lived feature branches in favor of small, frequent integrations, you replace the chaotic cycle of massive merge conflicts and code freezes with a steady, continuous trickle of small, safe, and fully tested updates.