Stacked diffs and tooling at Meta with Tomas Reimers

The episode delves into Meta's unique approach to internal developer tooling, exploring how it built its own tools like Fabricator, Sandcastle, and Butterflybot instead of relying on industry-standard solutions like GitHub. Tomas Reimers emphasizes the integration across these tools and how they promote efficiency in code reviews and development workflows. He explains the functionality of Fabricator as an internal code review tool and illustrates how Meta’s tools enable deep integration for tasks, monitoring translations, and version testing, creating a streamlined developer experience.

Tomas introduces the concept of stacked diffs at Meta, a method that allows developers to work on multiple branches for different features simultaneously, thereby managing code review bottlenecks more effectively. He details how this practice emerged and why it became essential within Meta, highlighting the advantages of creating smaller, manageable pull requests that are easier to review, ultimately accelerating the development process and enhancing collaboration.

In discussing Meta’s transition from polyrepos to monorepos, Tomas outlines the benefits of having a single repository for all code. He explains that this transition facilitates better collaboration, reduces dependency issues, and integrates more seamlessly with the tools used by developers. The conversation touches on the challenges that larger organizations face with multiple repositories and how unifying under a single monorepo can enhance productivity across teams.

Tomas shares insights on how AI tools are transforming software development, especially in enhancing code generation and deployment. He notes that while AI accelerates development, it also increases the volume of code that needs to be reviewed, thereby making code reviews even more critical. The discussion explores the need for maintaining high-quality code and accountability in the face of AI-generated outputs, suggesting that robust testing and thoughtful reviews will become increasingly important.

The episode discusses key engineering metrics often used by organizations to measure productivity and performance. Tomas highlights metrics like the number of pull requests, time to merge, and specifically a metric on the inactivity of pull requests during code review. These metrics give teams insights into their workflow efficiency and can trigger improvements in processes to enhance developer productivity.

Tomas narrates the journey of Graphite, from its initial focus on mobile release tools to identifying the greater need for better code review processes. He shares how feedback from former colleagues led to a pivot towards creating tools centered around stacked diffs, reflecting the real challenges developers face outside large tech companies. This transformation showcases the importance of adaptability within a startup environment.