Group versus Individual Review Requests: Tradeoffs in Speed and Quality at Mozilla Firefox

2026-01-04

arXiv.org

AI Summary

This study addresses the unclear mechanisms by which group-based versus individual reviewer assignment affects review speed and quality in code review. Drawing on shared task queue theory from management science, the authors introduce this framework to software engineering for the first time, analyzing approximately 66,000 code revisions from the Mozilla Firefox project through multivariate regression modeling and focus group interviews. The findings reveal that group-based assignment significantly reduces post-merge defect rates and enhances review quality, with negligible impact on review speed. Furthermore, it effectively promotes workload balancing and facilitates the onboarding of new reviewers, underscoring its distinct value not only for quality assurance but also for team capability development.

Technology Category

• Multiagent Systems: Teamwork
• Humans and AI: Planning and Decision Support for Human-Machine Teams
• Constraint Satisfaction and Optimization: Distributed CSP/Optimization

Application Category

• Economics, Online Markets and Human Computation: LLM based quality controls for crowd work
• Search and Retrieval-Augmented AI: Web evaluation methodologies and metrics
• Security and Privacy: Large-scale security measurements

Abstract

The speed at which code changes are integrated into the software codebase, also referred to as code review velocity, is a prevalent industry metric for improved throughput and developer satisfaction. While prior studies have explored factors influencing review velocity, the role of the review assignment process, particularly the `group review request', is unclear. In group review requests, available on platforms like Phabricator, GitHub, and Bitbucket, a code change is assigned to a reviewer group, allowing any member to review it, unlike individual review assignments to specific reviewers. Drawing parallels with shared task queues in Management Sciences, this study examines the effects of group versus individual review requests on velocity and quality. We investigate approximately 66,000 revisions in the Mozilla Firefox project, combining statistical modeling with practitioner views from a focus group discussion. Our study associates group reviews with improved review quality, characterized by fewer regressions, while having a negligible association with review velocity. Additional perceived benefits include balanced work distribution and training opportunities for new reviewers.

Problem

• code review
• review assignment
• group review
• review velocity
• software quality

Innovation

• group review request
• code review velocity
• review quality
• shared task queue
• software engineering