79: Building Android apps in Meta’s monorepository with Buck2
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/
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78: Generating 3D Worlds with AI
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
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ARCHIVE: What it's like to write code at Meta
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
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77: How to build a generic neuromotor interface
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
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76: From C to Rust on Mobile
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
Brought to you by Meta. In addition to remaining active in the open source community and conference circuit, this podcast offers another channel that allows us to highlight the technical work of our engineers who will discuss everything from low-level frameworks to end-user features. Throughout the podcast, Meta engineer Pascal Hartig (@passy) will interview developers in the company.
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