It's not just Not Invented Here Syndrome. Some technologies like CSS simply don't scale if you're building some of the largest websites on the planet with thousands of engineers committing to the same code base every day. StyleX is Meta's open-source solution for CSS at scale and allows atomic styling of components while deduplicating definitions for bundle size and exposing a delightfully simple API for developers.

Tune in to learn from Melissa, one of the StyleX maintainers how Open Source has acted as a force multiplier for the project, how interacting with other large companies adopting StyleX has been, and much more!

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 Pascal (https://mastodon.social/@passy, https://threads.net/@passy_). Fancy working with us? Check out https://www.metacareers.com/.

Links

• How AI Is Transforming the Adoption of Secure-by-Default Mobile Frameworks: https://engineering.fb.com/2025/12/15/android/how-ai-transforming-secure-by-default-mobile-frameworks-adoption/

• StyleX: https://stylexjs.com

• MTP 67: Measuring Developer Productivity with Diff Authoring Time: https://pca.st/pt4p4tv5

Timestamps

• Intro and news 0:06

• Introduction Melissa 1:47

• Why did we build our own styling system? 4:07

• StyleX API 5:36

• cx vs StyleX 7:37

• Component styling and priorities 10:38

• How StyleX evolved in the past seven years 15:20

• Community influence 19:33

• Open Source 24:07

• Challenges of OSS 27:02

• Managed breaking changes in OSS 29:48

• Measuring success for StyleX 32:04

• Packaging challenges 34:34

• StyleX competition 38:42

• Creating the StyleX roadmap 40:24

• Outro 43:15

You've likely heard of Meta Ray-Ban Display by now — but what's it actually like to work on it? In this episode, Pascal talks to Kenan and Emanuel about the exciting features of Meta's First-Gen Display Glasses and Neural Wristband, the engineering and product challenges they encountered during development, and their vision for future generations of these devices.

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 Pascal (https://mastodon.social/@passy, https://threads.net/@passy_). Fancy working with us? Check out https://www.metacareers.com/.

Links

• Pyrefly Beta: https://pyrefly.org/blog/pyrefly-beta/

• Pyrefly and Pydantic: https://pyrefly.org/blog/pyrefly-pydantic/

• Meta Ray-Ban Display: https://www.meta.com/gb/ai-glasses/meta-ray-ban-display/

Timestamps

• Intro 0:06

• Introduction Kenan 1:35

• Introduction Emanuel 5:03

• Roles and responsibilities 8:07

• What is Meta Ray-Ban Display? 11:13

• Memorable challenges: Clasps 15:52

• Memorable challenges: Display 19:24

• Celebrating incremental wins 23:51

• The feedback cycle in hardware engineering 26:29

• Open culture and dogfooding 31:39

• One-way doors 32:44

• Striving for quality and polish in fast-moving environments 36:25

• UI principles for AI glasses 40:15

• Future Plans 44:04

• Outro 46:53

• Blooper 47:49

In this episode, Pascal talks to Dharmesh J. (DJ) and Lisa about the vision for the open, scalable future of networking hardware for AI and to break down Meta's big announcements from the 2025 Open Compute Project (OCP) Summit. We dive into the OCP ecosystem, explore how AI is used to enhance our carbon modeling, and share our progress toward achieving Net Zero emissions across all scopes by 2030.

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 Pascal (https://mastodon.social/@passy, https://threads.net/@passy_). Fancy working with us? Check out https://www.metacareers.com/.

Links

• OCP: https://www.opencompute.org/

• OCP Summit 2025: https://engineering.fb.com/2025/10/13/data-infrastructure/ocp-summit-2025-the-open-future-of-networking-hardware-for-ai/

• How Meta Is Leveraging AI To Improve the Quality of Scope 3 Emission Estimates for IT Hardware: https://engineering.fb.com/2025/10/14/data-center-engineering/how-meta-is-leveraging-ai-to-improve-the-quality-of-scope-3-emission-estimates-for-it-hardware/

Timestamps

• Intro 0:06

• Introduction Lisa 1:49

• Introduction DJ 3:16

• What is OCP? 4:04

• OCP's scale 5:24

• Open vs closed hardware ecosystems 9:26

• Examples of OCP projects 11:33

• Sustainability in OCP 14:08

• How did you get into OCP? 15:59

• Marrying infrastructure growth with sustainability 19:05

• Emissions scopes and tracking 25:07

• Measuring scope 3 26:06

• What components embed the most carbon? 30:47

• DFE vs DFS 32:34

• Hardware reuse 33:39

• Outro 37:48

How do you keep Android build times under control when your codebase spans tens of thousands of modules and millions of lines of Kotlin? In this episode, Pascal talks with Iveta, Navid, and Joshua from Meta's Android Developer Experience team about the technical strategies that help Meta's engineers stay productive at scale.

We discuss approaches like source-only ABIs and incremental compilation – clever solutions that have helped us tackle the challenges of building fast in a monorepo, as well as what you can do to keep your builds fast with Buck2.

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 Pascal (https://mastodon.social/@passy, https://threads.net/@passy_). Fancy working with us? Check out https://www.metacareers.com/.

Timestamps

• Intro 0:06

• Introducing Iveta 2:09

• Introducing Joshua 3:29

• Introducing Navid 4:00

• Android DevX Team 4:36

• The challenges of build speed 6:28

• Buck2 and Android 7:34

• How to add new language support to Buck2 9:01

• What's new in Open Source? 11:02

• Optimising Kotlin builds 12:55

• Source-only ABI 14:25

• Developer restrictions 17:33

• From Jasabi to Kosabi 20:33

• Strategies for keeping builds fast 22:08

• Working with big modules 23:00

• Bringing incremental Kotlin compilation to Buck2 24:48

• Speed improvements 28:52

• Third-party library upgrades 30:54

• What's next? 33:56

• Outro 36:14

Links

• Meta Connect 2025 Developer Talks: https://www.youtube.com/playlist?list=PLb0IAmt7-GS2cONiFVhtdKWEsyNkF6uUP

• Buck2: https://buck2.build/

• Incremental Kotlin compilation at Meta: https://engineering.fb.com/2025/08/26/open-source/enabling-kotlin-incremental-compilation-on-buck2/

• Blog post about Jasabi (the Java counterpart to Kosabi): https://engineering.fb.com/2017/11/09/android/rethinking-android-app-compilation-with-buck/

• Kotlin Conf talk about source-only ABI compilation: https://2025.kotlinconf.com/talks/857571/

• Meta Connect 2025 Developer Talks: https://www.youtube.com/playlist?list=PLb0IAmt7-GS2cONiFVhtdKWEsyNkF6uUP

• Buck2: https://buck2.build/

• Incremental Kotlin compilation at Meta: https://engineering.fb.com/2025/08/26/open-source/enabling-kotlin-incremental-compilation-on-buck2/

• Blog post about Jasabi (the Java counterpart to Kosabi): https://engineering.fb.com/2017/11/09/android/rethinking-android-app-compilation-with-buck/

• Kotlin Conf talk about source-only ABI compilation: https://2025.kotlinconf.com/talks/857571/

Creating 3D assets can be daunting, but does it have to be? Mahima and Rakesh are on a quest to democratize 3D content creation with AssetGen, a foundation model for 3D. They discuss the challenges of training such a model given the scarcity of available data and how large language models have unlocked key solutions. As if that weren't enough, they're also tackling the ambitious goal of generating entire worlds from a simple prompt. Tune in to learn more!

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 Pascal (https://mastodon.social/@passy, https://threads.net/@passy_, @passy.bsky.social). Fancy working with us? Check out https://www.metacareers.com/.

Links

• Horizon Worlds Desktop Editor: https://developers.meta.com/horizon-worlds/advanced-tools

• Horizon Worlds Studio: https://developers.meta.com/horizon-worlds/studio/application

• Meta Ray-Ban Display: https://www.meta.com/gb/ai-glasses/meta-ray-ban-display/

• MTP 77 - How to build a human-computer interface for everyone: https://engineering.fb.com/2025/08/04/virtual-reality/building-a-human-computer-interface-for-everyone-meta-tech-podcast/

Timestamps

• Intro 0:06

• Introduction Mahima 1:39

• Introduction Rakesh 2:57

• Team mission 3:26

• Why is 3D content hard to create? 5:15

• The Metaverse 7:49

• Tooling vision in Horizon Worlds 10:31

• AssetGen Architecture 15:27

• Consolidating models 18:25

• From assets to worlds 19:22

• Time to generate 24:46

• Feedback loop 26:41

• What's the market for AssetGen 29:49

• What's available today? 31:26

• What's next? 32:11

• Outro 35:24

To not leave you without an episode for August, Pascal brings you an episode from the Archive. Back in August 2023 for Episode 55, Pascal spoke with Katherine and returning guest Dustin, two software engineers at Meta about how to ship code at Meta. Why do we have a monorepo? Why and how do we do pre-commit code review? What does our CI infrastructure look like? Get the answers to these questions and many more in this episode of the Meta Tech Podcast.

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 Pascal (https://mastodon.social/@passy, https://threads.net/@passy_). Fancy working with us? Check out https://www.metacareers.com/.

Links

• The evolution of Facebook's iOS app architecture - Engineering At Meta: https://engineering.fb.com/2023/02/06/ios/facebook-ios-app-architecture/

• Episode 47: Source control at Meta - https://pca.st/episode/429e9f38-6537-43e3-b929-fbeeda326ed5

Timestamps

• Intro 0:06

• Intro Katherine 1:55

• Dustin's Origin Story 4:38

• Topic Intro 6:28

• Why Monorepo(s) 7:18

• What Makes Monorepos Hard? 12:15

• Why do we Have so Many Files? 17:31

• Who Owns Stuff? 25:29

• Life of a Diff 28:58

• Writing Bots Writing Code Writing Bots 34:16

• Finding Reviewers 38:46

• Why Are Things Not Constantly on Fire? 41:43

• Outro 47:47

• Outtakes 48:46

Join Pascal as he explores the groundbreaking world of generic neuromotor interfaces with Jesse, Lauren, and Sean. Discover how these technologies enable control of devices with just a flick of the wrist or even a simple intention to move. We'll discuss the role of AI in eliminating the need for personalised training, the differences between non-invasive interfaces and their predecessors, and the exciting implications for accessibility. Don't miss this deep dive into the future of human-computer interaction.

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 Pascal (https://mastodon.social/@passy, https://threads.net/@passy_). Fancy working with us? Check out https://www.metacareers.com/.

Timestamps

• Intro 0:06

• Jesse introduction 1:29

• Lauren introduction 2:42

• Sean introduction 3:29

• Team's mission statement 3:49

• What's a neuromotor interface? 4:24

• Paper overview 5:29

• Non-invasive interfaces 7:50

• How to make it generic 9:42

• Design tradeoffs 11:29

• Real-world model performance 14:21

• Feedback cycle 16:22

• LLMs and EMG 17:22

• Handwriting vision 18:39

• Working with product 20:55

• EMG for accessibility 22:25

• How Meta helps 25:53

• Open-source repos 28:02

• What's next? 28:45

• Outro 30:51

Links

• A generic non-invasive neuromotor interface for human-computer interaction - Nature - https://www.nature.com/articles/s41586-025-09255-w

• How the low-vision community embraced AI smart glasses - The Verge - https://www.theverge.com/the-vergecast/701018/ray-ban-meta-smart-glasses-be-my-eyes-ceo-accessibility-tech

• MKBHD on Orion - https://www.youtube.com/watch?v=G0eKzU_fV00

What happens when decades-old C code, powering billions of daily messages, starts to slow down innovation? In this episode, we talk to Meta engineers Elaine and Buping, who are in the midst of a bold, incremental rewrite of one of our core messaging libraries—in Rust. Neither came into the project as Rust experts, but both saw a chance to improve not just performance, but developer experience across the board.

We dig into the technical and human sides of the project: why they took it on, how they're approaching it without a guaranteed finish line, and what it means to optimise for something as intangible (yet vital) as developer happiness. If you've ever wrestled with legacy code or wondered what it takes to modernise systems at massive scale, this one's for you.

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 Pascal (https://mastodon.social/@passy, https://threads.net/@passy_). Fancy working with us? Check out https://www.metacareers.com/.

Timestamps

• Intro 0:06

• Introduction Elaine 1:54

• Introduction Buping 2:49

• Team mission 3:15

• Scale of messaging at Meta 3:40

• State of native code on Mobile 4:40

• Why C, not C++? 7:13

• Challenges of working with C 10:09

• State of Rust on Mobile 18:10

• Why choose Rust? 23:36

• Prior Rust experience 28:55

• Learning Rust at Meta 34:14

• Challenges of the migration 37:47

• Measuring success 42:09

• Hobbies 45:15

• Outro 46:41

Pyrefly is a faster, open-source Python type checker written in Rust, succeeding Pyre. But what prompted the rewrite and what besides the language choice ended up making it faster? Host Pascal talks to Maggie, Rebecca and returning guest Neil about the unexpected complexities of building an incremental type checker that scales to mono repositories in episode 75.

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 Pascal (https://mastodon.social/@passy, https://threads.net/@passy_). Fancy working with us? Check out https://www.metacareers.com/.

Links

• Pyrefly: https://pyrefly.org/

• Pyre: https://pyre-check.org/

• Ruff: https://github.com/astral-sh/ruff

• PEP 484: https://peps.python.org/pep-0484/

Timestamps

• Intro 0:06

• Rebecca Introduction 1:45

• Maggie Introduction 2:45

• Neil (Re-)Introduction 3:12

• Team Mission 3:56

• History of Typing in Python 4:29

• The State of Typed Python at Meta 5:32

• fbcode 6:02

• Original Motivation for building Pyre 6:19

• Justifying the Rewrite 7:48

• Pyrefly vs the Rest 9:41

• Why Rust? 10:45

• Fearless Concurrency 12:02

• Why is it faster? 12:37

• Python community and Rust 14:57

• Pyrefly wasm crate 15:46

• Upgrade experience 17:34

• Type checking differences 19:12

• IDE experience 21:31

• State of Pyrefly at Meta 22:27

• Being open-source-first 23:36

• Open-source challenges 25:06

• Unexpected challenges 26:39

• Outro 31:05

To ensure that everyone has access to resilient, high-speed and low-latency connections to Meta services, no matter where in the world they are, Meta makes large-scale investments into subsea cable infrastructure. The recently announced Project Water worth will, Once complete, reach five major continents and span over 50,000 km (longer than the Earth's circumference), making it the world's longest subsea cable project using the highest-capacity technology available.

In this episode, host Pascal talks with another Pascal and his colleague Andy who are involved at every stage of these projects and share the surprising challenges one has to deal with when working on the largest subsea cable project in the world.

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 Pascal (https://mastodon.social/@passy, https://threads.net/@passy_). Fancy working with us? Check out https://www.metacareers.com/.

Links

• Project Waterworth: https://engineering.fb.com/2025/02/14/connectivity/project-waterworth-ai-subsea-infrastructure/

Timestamps

• Intro 0:06

• Introduction Andy 2:14

• Introduction Pascal 3:21

• Why do we build our own subsea cable infrastructure? 4:15

• Current state of Meta-owned subsea cables 6:20

• Project Waterworth 7:40

• Why invest in more subsea cables? 9:00

• What does a cable look like? 11:14

• The process of laying subsea cable 16:39

• Unexpected findings on the ocean floor 19:25

• Shallow vs deep ocean 21:12

• Merging different cable types 24:00

• What happens when a cable breaks? 25:04

• Memorable challenges 27:42

• Cable capacity 29:51

• The long history of subsea cables 33:07

• What's next? 36:27

• Outro 39:02