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
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75: Open-sourcing Pyrefly - A faster Python type checker written in Rust
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 Â
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74: Taking the plunge - The engineering journey of building a Subsea Cable
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
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73: Mobile GraphQL at Meta in 2025
Join Pascal and Sabrina on the latest Meta Tech Podcast episode as they discuss the evolution and future of GraphQL. From client-side consistency to innovative APIs, learn how GraphQL is making developers' lives easier and enhancing user experiences. Discover surprising insights into the challenges of building a mobile GraphQL platform and how it's transforming product development at Meta.  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 GraphQL: https://graphql.org/ Relay: https://relay.dev/ Sabrina at GraphQL Conf 2024: https://www.youtube.com/watch?v=PGBC-0E-kco Timestamps Intro 0:06 Introduction Sabrina 1:42 Sabrina's team 2:47 What's GraphQL? 3:18 Relay and Mobile GraphQL Clients 4:01 GraphQL Consistency Engine 4:54 Pando Mobile GraphQL Client 7:16 Interfacing with Pando 8:03 Code generation 9:14 Inventing new features 10:43 The hidden complexity behind pagination 11:52 Working inside the GraphQL spec 16:00 Complexity tradeoffs 18:30 State of GraphQL at Meta 21:16 Measuring success 24:58 Optimistic Mutations 27:31 Collaboration model 31:42 Preventing early adoption 34:43 The challenge of migrating FBApp 37:10 What's next for mobile GraphQL? 40:22 Outro 41:54 Â
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72: Multimodal AI for Ray-Ban Meta glasses
In this episode of the Meta Tech Podcast, host Pascal sits down with Shane, a research scientist at Meta, to explore the cutting-edge research behind Ray-Ban Meta glasses. Shane shares insights from his seven-year journey at Meta, where he focuses on computer vision and multimodal AI within the Wearables AI organization. Tune in to learn how Shane's team is pioneering foundational models for Ray-Ban Meta glasses, tackling unique challenges, and pushing the boundaries of AI-driven innovation. Discover how multimodal AI is transforming user experiences and get a glimpse into the future of wearable technology. Whether you're an engineer, a tech enthusiast, or simply curious about the latest advancements, there is something for everyone in this episode. 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 AnyMAL: An Efficient and Scalable Any-Modality Augmented Language Model - https://arxiv.org/abs/2309.16058 Be My Eyes Programme: https://www.forbes.com/sites/stevenaquino/2024/10/11/inside-the-be-my-eyes-meta-collaboration-and-the-allure-to--impact-humanity/ Meta Open Source on Threads: https://www.threads.net/@metaopensource CacheLib: https://cachelib.org/ Meta’s AI-Powered Ray-Bans Are Life-Enhancing for the Blind - Wall Street Journal: https://www.wsj.com/tech/ai/metas-ai-powered-ray-bans-are-life-enhancing-for-the-blind-3ae38026 Timestamps Intro 0:06 OSS News 0:56 Introduction Shane 1:30 The role of research scientist over time 3:03 What's Multimodal AI? 5:45 Applying Multimodal AI in Meta's products 7:21 Acoustic modalities beyond speech 9:17 AnyMAL 12:23 Encoder zoos 13:53 0-shot performance 16:25 Iterating on models 17:28 LLM parameter size 19:29 How do we process a request from the glasses? 21:53 Processing moving images 23:44 Scaling to billions of users 26:01 Where lies the optimisation potential? 28:12 Incorporating feedback 29:08 Open-source influence 31:30 Be My Eyes Programme 33:57 Working with industry experts at Meta 36:18 Outro 38:55
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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