- Developers
- Learn how Meta experiments with language features like type systems to improve developer productivity and code quality.
- Business
- Understand how metrics and experimentation can be used to optimize developer workflows and potentially reduce engineering costs.
This episode provides a detailed look at internal Meta tooling for developer productivity experiments.
69: To type or not to type — measuring productivity impact with DAT
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From Subvolts
Summary and analysis by Subvolts editorial, AI-assisted.
Meta Tech Podcast episode 69 features host Pascal Harris discussing Diff Authoring Time (DAT), a system for measuring productivity impact. The episode explores whether programming type systems increase typing or actual productivity, using internal Meta codebase experiments to answer these questions. It also touches on Hack language and code sharing frameworks.
This episode discusses how Meta tests if adding programming 'types' makes developers faster or just makes them type more. They use a system called DAT to measure this on their own code. This helps them understand how to build better tools for programmers.
This episode offers a look into how Meta uses metrics to experiment with developer productivity, specifically focusing on the impact of programming language features like type systems. It's relevant for software engineers and engineering managers interested in developer experience and language design. The discussion on internal tooling and experimentation connects to broader trends in AI development, where optimizing developer workflows is crucial for accelerating research and product cycles.
- HostPascal Harris
- Episode Title: 69: To type or not to type — measuring productivity impact with DAT
- Show: Meta Tech Podcast
- Length: 40 minutes
- System Discussed: Diff Authoring Time (DAT)
- Language Mentioned: Hack language
Do types actually make you more productive or is it just more typing for you to do on the keyboard? That's just one of the questions we managed to answer at least on a small scale with Diff Authoring Time or DAT, here at Meta. Want to know how we leverage metrics to run experiments on productivity in our internal codebase? Tune in to episode 69.
Got feedback? Send it to us on Threads (https://threads.net/@metatechpod), Instagram (https://instagram.com/metatechpod) and don't forget to follow our host @passy (https://mastodon.social/@passy, and https://threads.net/@passy_). Fancy working with us? Check out https://www.metacareers.com/.
Links
- Hack language: https://hacklang.org/
Timestamps
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Intro 0:06
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Henri Intro 1:45
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Ian Intro 3:13
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Moritz Re-Intro 3:28
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DAT Recap 3:48
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What is Hack? 4:20
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Inner and outer loop 14:13
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Experimenting with language features 17:47
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Code sharing frameworks at Meta 27:43
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Measuring framework productivity 29:01
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Will we see more experiments? 34:23
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Time savings from code sharing 37:28
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Outro 39:03
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Blooper 39:52
- Type systems
- In programming, type systems help catch errors by checking the kind of data variables hold.
- Ways to check if data is the right kind (like numbers or text) to prevent mistakes.
- Inner and outer loop
- In software development, the 'inner loop' refers to the rapid cycle of writing, testing, and debugging code, while the 'outer loop' involves broader processes like deployment and integration.
- The quick cycle of writing and testing code versus the slower process of putting it all together.
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Questions people ask
- What is Diff Authoring Time (DAT)?
- DAT is a system Meta uses to run experiments and measure the productivity impact of programming language features, like type systems, on their internal codebase.
- What is Hack language?
- Hack is a programming language developed by Meta, designed to improve developer productivity and code quality.
Page generated Oct 19, 2026. Summaries are Subvolts' own; the audio, artwork and notes belong to Meta.

