Trunk Based Development

How Large Pull Requests Are Killing Your Delivery Speed

In many software teams, the pattern is all too familiar: a developer works for days on a feature branch, opens a Pull Request with hundreds of lines changed, and hopes someone finds the time to review it. The PR sits in the queue. The review becomes superficial. The merge to main gets postponed. And the release? That becomes a project in itself.

Trunk Based Development (TBD) is a direct answer to this problem. It is a branching strategy where all developers integrate into one shared branch (the trunk, or main) multiple times a day. It sounds simple. It is. But the implications are profound.

The Problem with Large Pull Requests

From Feature Branch to Fear

Feature branches were invented to provide isolation: you work independently without disrupting others. But what starts as a convenient separation quickly grows into a silo. Developers work for weeks on their own branch, and the distance from main keeps growing.

When the PR is finally opened, the result is overwhelming: 800 changed files, 3,000 lines of diff, changes mixed together across business logic, refactoring, and bug fixes. Who is going to review that? And how thoroughly?

A PR with 1,000 lines is no longer a Pull Request. It is a surrender.

Reviews That Mean Nothing

The reality of large PRs is that they are rarely reviewed seriously. It simply takes too much time. Reviewers scroll through the diff, leave a few surface-level comments, and approve the PR to clear it from the queue. The quality gate that the review phase was supposed to provide simply evaporates.

The side effects are predictable. Architectural mistakes get discovered too late. Business logic is not understood by the rest of the team. Technical debt accumulates silently. Knowledge stays locked in individual developers' heads.

What started as a safety mechanism becomes a rubber stamp.

Large PRs Lead to Late Releases

The Merge Becomes a Project

The longer a branch lives, the greater its divergence from main. When a merge is attempted after two weeks, merge conflicts are almost guaranteed, and not just syntactic ones. Semantic conflicts too: two developers who independently modified the same piece of logic in different ways.

The merge itself now takes hours. After that comes an extensive round of testing and verification. The "ready to release" status keeps sliding further away.

Release Anxiety

In teams working with large PRs and long-lived branches, release anxiety is inevitable. The question "are we ready to release?" gets met with hesitation, because nobody knows exactly what is in the release. So much has changed at once that the risk of regression feels very real.

Teams start releasing less frequently as a result. And the less frequently you release, the more changes accumulate in the next release, which makes the next release even scarier. A vicious cycle takes hold where the act of releasing becomes something to dread rather than something routine.

Nobody Merges to Main Anymore

Long-lived branches create a culture of avoidance. Developers stop merging to main regularly because they fear what they will encounter when they do. Integration events become rare, high-stakes operations.

The consequences compound over time. The main branch no longer reflects the current state of the codebase. Continuous integration becomes impossible in any meaningful sense. The team loses the habit, and eventually the confidence, to ship.

This is the paradox of trying to reduce risk through isolation: the longer you wait, the more risk you accumulate.

Trunk Based Development as the Solution

TBD flips this dynamic entirely. Developers work in small, focused increments. They push to main, or to very short-lived branches that are merged within hours rather than days. Every push triggers the CI pipeline. Every integration is a small, verifiable event.

The benefits are immediate. PRs stay small enough to review meaningfully (under 200 lines is a reasonable target). Reviewers can engage deeply with the intent of the change. Merge conflicts are rare and easy to resolve. The main branch is always in a releasable state.

Feature Flags as an Enabler

One of the most common objections to TBD is: "But my feature isn't finished yet. I can't ship half a feature." Feature flags solve this cleanly. Incomplete work is merged behind a flag that is off in production. The code integrates continuously. The feature ships when it is ready. Development and deployment are decoupled.

Releasing Without Anyone Noticing

One of the most underappreciated benefits of frequent, small releases is the ability to deploy without disruption. If your infrastructure supports zero-downtime deployments, and most modern Kubernetes-based setups do, you can release multiple times a day without your consumers ever noticing.

The key is proper pod scaling. When you deploy a new version, you scale up new pods running the updated code before scaling down the old ones. Traffic shifts gradually. There is no downtime. From the perspective of any consuming party, the service never went offline.

Old pods:   [v1] [v1] [v1]
Deploying:  [v1] [v1] [v2]   <- new pod starts taking traffic
Done:       [v2] [v2] [v2]   <- old pods terminated

This approach, whether through rolling deployments or blue/green strategies, transforms a release from a high-risk event into a non-event. And when releases are non-events, teams stop being afraid of them.

You Get Better By Doing It More Often

There is a second-order effect here that is easy to overlook. The prerequisite for seamless deployment is a deployment landscape that actually works: health checks properly configured, readiness probes in place, a reliable pipeline, and fast rollback.

Most teams do not have this from day one. But every deployment is a test of your setup. When you release once a month, problems in your pipeline surface infrequently and get fixed slowly. When you release ten times a week, you expose those problems constantly and are forced to fix them.

Frequent releasing makes your deployment infrastructure robust. The more you do it, the better you get at it. Teams that deploy daily have better pipelines, faster feedback loops, and more confidence in their tooling than teams that deploy monthly. Not because they started with better infrastructure, but because they improved it through repetition.

Making the Shift

Moving to TBD is not just a tooling change. It is a cultural one. It requires discipline around small commits, where every commit is a coherent and reviewable unit of work. It requires trust in the CI pipeline, so that a passing build is sufficient to merge. It requires a working deployment landscape with health checks, rollback strategy, and monitoring in place. And it requires feature flags for incomplete work, separating deployment from feature activation and removing the last excuse for long-lived branches.

The reward is substantial. Teams that practice TBD release more often, with less stress, with higher confidence, and with a much tighter feedback loop between writing code and seeing it in production.

The goal is not to release fast for the sake of it. The goal is to make releasing so routine, so small, and so safe that it stops being something you plan for and becomes something you simply do.

"If it hurts, do it more often." — Jez Humble, Continuous Delivery