Deep-dive discussions with the smartest developers we know, explaining what they're working on, how they're trying to move the industry forward, and what we can learn from them. You might find the solution to your next architectural headache, pick up a new programming language, or just hear some…
How would you manage 30 million lines of PHP? You can't rewrite it - you'd be fired long before you delivered. That was the problem facing Facebook around 2011, and their answer was to add a type system, giving birth to the Hack language. But adding types to PHP turned out to be the easy part. The hard part was building a type checker that developers used to "edit, save, refresh" would actually tolerate. So how do you type-check tens of millions of lines of code fast enough that nobody notices? Julien Verlaguet co-designed Hack at Facebook, and has spent the fifteen years since chasing a…
Building something people actually want is supposed to be the happy ending. But it arrives with a bill attached: feature requests you didn't ask for, pull requests you'd rather not maintain forever, users demanding the one thing you swore you'd never build, and — if you're unlucky — a company where the sales team quietly starts deciding what engineering works on. DuckDB has spent the last two and a half years working through that list. So how do you stay a database engineering team when success keeps trying to turn you into something else? Hannes Mühleisen, co-creator of DuckDB, is back to…
My guest this week is James Brown, an engineering lead at Schroders, and that's a useful vantage point — asset managers carry all the regulation and organisational weight of a bank, mixed with the first-to-market pressure of a startup. James starts with his own "Claude mania": months of agents running around the clock, and the wave of anxiety that hit him one morning walking to the shop without one running at home. From there, Clair — the plugin he's building to give coding agents proximal awareness of each other, using git orphan branches as a zero-infrastructure message bus; why AI behaves…
There's a problem that's bugged the database industry since the 1980s: you run an expensive query over millions of rows, cache the result, and then a single new row arrives. Logically that's one small update, but most engines throw the cached answer away and recompute everything from scratch. Some will handle changes incrementally, but only for "simple" queries - and the rules for what counts as simple are arbitrary and brittle. So can you incrementally maintain *any* SQL query, no matter how complex? For decades the answer was no. Then an award-winning paper called DBSP proved that the…
AI is changing the way we all build software — that much seems clear. But the landscape is moving so fast that even the people paid to keep up are struggling. MCP or skills? Fine-tune or just prompt? LangChain or let a thousand agents loose? With almost 70 competing technologies and a shelf life of maybe six months on any advice, how do you figure out what's actually worth your time? Henry Garner is CTO of JUXT, a consultancy with about 150 senior engineers working at the coalface of AI-assisted development, including building AI platforms for tier-one banks. JUXT publishes a quarterly AI…
I have a theory that only bad projects get finished — good ones keep finding new things to do. Asciinema is a case in point. What started as a way to share terminal sessions with friends has, over 14 years, grown into a full suite of tools covering recording, hosting, playback, and live streaming — and been rebuilt multiple times along the way. So what does it actually take to record and replay a terminal session faithfully in a browser? Joining us for this conversation is Marcin Kulik, Asciinema's creator. The project's architecture has passed through almost every interesting corner of…
Eighteen months ago, Tyler Cloutier appeared on the show with what sounded like an ambitious (some might say crazy) plan: build a new distributed database from scratch, then use it to power a massively multiplayer online game. That's two of the hardest problems in software, tackled simultaneously. But sometimes the best infrastructure comes from solving your own impossible problems. The game, Bitcraft, has now launched on Steam. SpacetimeDB has hit version 1.0. And Tyler returns to share what actually happened when theory met production reality. We cover the launch day performance disasters…
SQLite is embedded everywhere - phones, browsers, IoT devices. It's reliable, battle-tested, and feature-rich. But what if you want concurrent writes? Or CDC for streaming changes? Or vector indexes for AI workloads? The SQLite codebase isn't accepting new contributors, and the test suite that makes it so reliable is proprietary. So how do you evolve an embedded database that's effectively frozen? Glauber Costa spent a decade contributing to the Linux kernel at Red Hat, then helped build Scylla, a high-performance rewrite of Cassandra. Now he's applying those lessons to SQLite. After…
How do you build systems with AI? Not code-generating assistants, but production systems that use LLMs as part of their processing pipeline. When should you chain multiple agent calls together versus just making one LLM request? And how do you debug, test, and deploy these things? The industry is clearly in exploration mode—we're seeing good ideas implemented badly and expensive mistakes made at scale. But Google needs to get this right more than most companies, because AI is both their biggest opportunity and an existential threat to their search-based business model. Christina Lin from…
How do you monitor distributed systems that span dozens of microservices, multiple languages, and different databases? The old approach of gathering logs from different machines and recompiling apps with profiling flags doesn't scale when you're running thousands of servers. You need a unified strategy that works everywhere, on every component, in every language—and that means tackling the problem from the kernel level up. Mohammed Aboullaite is a backend engineer at Spotify, and he joins us to explore the latest in continuous profiling and observability using eBPF. We dive into how eBPF…
Git might be the most ubiquitous tool in software development, but that doesn't mean it's perfect. What if we could keep Git compatibility while fixing its most frustrating aspects—painful merges, scary rebases, being stuck in conflict states, and the confusing staging area? This week we're joined by Martin von Zweigbergk, creator of Jujutsu (JJ), a Git-compatible version control system that takes a fundamentally different approach. Starting from a simple idea—automatically snapshotting your working copy—Martin has built a tool that reimagines how we interact with version control. We explore…
Getting new technology adopted in a large organization can feel like pushing water uphill. The best tools in the world are useless if we're not allowed to use them, and as companies grow, their habits turn into inertia, then into "the way we've always done things." So how do you break through that resistance and get meaningful change to happen? This week's guest is Dov Katz from Morgan Stanley, who specializes in exactly this challenge - driving developer productivity and getting new practices adopted across thousands of developers. We explore the art of organizational change from every…
How confident are you when your test suite goes green? If you're honest, probably not 100% confident - because most bugs come from scenarios we never thought to test. Traditional testing only catches the problems we anticipate, but the 3am pager alerts? Those come from the unexpected interactions, timing issues, and edge cases we never imagined. In this episode, Will Wilson from Antithesis takes us deep into the world of autonomous testing. They've built a deterministic hypervisor that can simulate entire distributed systems - complete with fake AWS services - and intelligently explore…
How would you build a Heroku-like platform from scratch? This week we're diving deep into the world of cloud platforms and infrastructure with Anurag Goel, founder and CEO of Render. Starting from the seemingly simple task of hosting a web service, we quickly discover why building a production-ready platform is far more complex than it appears. Why is hosting a Postgres database so challenging? How do you handle millions of users asking for thousands of different features? And what's the secret to building infrastructure that developers actually want to use? We explore the technical…
How hard is it to write a good database engine? Hard enough that sometimes it takes several versions to get it just right. Paul Dix joins us this week to talk about his journey building InfluxDB, and he's refreshingly frank about what went right, and what went wrong. Sometimes the real database is the knowledge you pick up along the way.... Paul walks us through InfluxDB's evolution from error logging system to time-series datasbase, and from Go to Rust, with unflinching honesty about the major lessons they learnt along the way. We cover technical details like Time-Structure Merge Trees, to…
If AI coding tools are here to stay, what form will they take? How will we use them? Will they be just another window in our IDE, will they push their way to the centre of our development experience, displacing the editor? No one knows, but Zach Lloyd is making a very interesting bet with the latest version of Warp. In this deep dive, Zach walks us through the technical architecture behind agentic development, and how it's completely changed what he & his team have been building. Warp has gone from a terminal built from scratch, to what they're calling an "agentic development environment" -…
Ever wondered why data integration is still such a nightmare in 2025? Marty Pitt has built something that might finally solve it. TaxiQL isn't just another query language - it's a semantic layer that lets you query across any system without caring about field names, API differences, or where the data actually lives. Instead of writing endless mapping code between your microservices, databases, and APIs, you describe what your data *means* and let TaxiQL figure out how to get it. In this conversation, Marty walks through the "All Powerful Spreadsheet" moment that sparked TaxiQL, how semantic…
At 23, Isaac is already jaded about software reliability - and frankly, he's got good reason to be. When your grandmother can't access her medical records because a username change broke the entire system, when bugs routinely make people's lives harder, you start to wonder: why do we just accept that software is broken most of the time? Isaac's answer isn't just better testing - it's a whole toolkit of techniques working together. He's advocating for scattering "little bombs" throughout your code via runtime assertions, adding in the right amount of static typing, building feedback loops…
How do you retrofit a clustered data-processing system to use cheap commodity storage? That's the big question in this episode as we look at one of the many attempts to build a version of Kafka that uses object storage services like S3 as its main disk, sacrificing a little latency for cheap, infinitely-scalable disks. There are several companies trying to walk down that road, and it's clearly big business - one of them recently got bought out for a rumoured $250m. But one of them is actively trying to get those changes back into the community, as are pushing to make Apache Kafka speak…
Java's has been evolving faster than any 30 year old language has a right to do, and there's probably no-one more pleased about it than my guest this week - Josh Long. He's a Java & Kotlin programming, a JVM enthusiast in general, and an advocate for Spring, and he has chapters full of news about what's been happening in Javaland over the past few years. Everything from new threading models to C interop changes, custom primitives to high performance computing and all the ways in which Java is modernising for age of AI workloads. If you're out of touch with the latest in the JVM, or don't…
I'm joined this week by one of the authors of Apache Kafka In Action, to take a look at the state of Kafka, event systems & stream-processing technology. It's an approach (and a whole market) that's had at least a decade to mature, so how has it done? What does Kafka offer to developers and businesses, and which parts do they actually care about? What have streaming data systems promised and what have they actually delivered? What's still left to build? – Apache Kafka in Action: https://www.manning.com/books/apache-kafka-in-action Pat Helland, Data on the Inside vs Data on the Outside:…
Building a database is a serious undertaking. There are just so many parts that you have to implement before you even get to a decent prototype, and so many hours of work before you could begin working on the ideas that would make your database unique. Apache DataFusion is a project that hopes to change all that, but building an extensible, composable toolkit of database pieces, which could let you build a viable database extremely quickly, and then innovate from that starting point. And even if you're not building a database, it's a fascinating project to explain how databases are built.…
Jupyter's become an incredibly popular programming and data science tool, but how does it actually work? How have they built an interactive language execution engine? And if we understand the architecture, what else could it be used for? Joining me to look inside the Jupyter toolbox are Afshin Darian and Sylvain Corlay, two of Jupyters long-standing contributors and project-steerers. They've going to take us on a journey that starts with today's userbase, goes through the execution protocol and ends with a look at what Jupyter will be in the future - an ambitious framework for interactive,…
Ever since we invented makefiles, the programming world has been wrestling with the problem of building software stacks reliably. This week we're going to look at one of the most ambitious solutions available - Nix. Nix tries to do everything from invoking your compiler to installing your language, and even providing your operating system. But how does it work in theory, and how well does it work in practice? Joining me to discuss is Julian Arni, a Nix-enthusiast and creator of a build/test/deploy service called Garnix. Nix has been one of my go-to tools for years - I hope it'll find its way…
Graphite is a new image editor with an interesting architecture - it's a classic UI-driven app, an image-manipulation language, and a library of programmable graphics primitives that any Rust coder could use, extend or add to. The result is something that you can use like Photoshop or Inkscape, or make use of in batch pipelines, a bit like ImageMagick. Joining me to discuss it are Keavon Chambers & Dennis Kobert, who are hammering away on building a project that's potentially as demanding as Photoshop, but with a more ambitious architecture. How can they hope to compete? Perhaps in the short…
ReScript is a strongly-typed programming language that compiles to JavaScript, and that puts it squarely in competition with TypeScript. So why would a JavaScript developer choose to learn it next? What does it offer that makes it a tempting proposition? And how are the ReScript developers making life easier for anyone who wants to make the switch? To answer all these questions and more, I'm joined this week by Gabriel Nordeborn, one of ReScript's compiler contributors. -- ReScript: https://rescript-lang.org/ ReScript & React: https://rescript-lang.org/docs/react/latest/introduction…
Trustfall is a library based on a simple question - what happens if we can query absolutely anything? If you could join REST APIs and databases with filesystems and dockerfiles? It's possible in theory because those are all just datasources. Predrag Gruevski is trying to make it easy by building a universal query engine, with pluggable datasources, all in Rust. This week we dive into Trustfall to figure out how it works. How do you model nearly anything as a datasource? How do you make it easy to extend? And what does it take to optimize a query that's going to be spread out over multiple…
Dimitris Kyriakoudis is a researcher, programmer and musician who's combining all three talents to build dedicated music hardware. Specifically a device called the µseq, which reads Lisp programs and uses them to drive synthesizers to make music. In this episode we go through the full platform that he's building, from soldering resistors to an RPi chip, up through writing a Lisp interpreter, to the design ideas that make Lisp a good choice for composing both software and music. – uSeq Homepage: https://www.emutelabinstruments.co.uk/useq/ Emute Lab's Homepage: https://www.emutelab.org/ Buy a…
If you want to build really large software systems well, you have to stop thinking of them as just software systems. Beyond a certain size, everything your software touches becomes part of the wider system. You're part of the system, your users are part of the system, and every other employee & department & priority eventually forms part of that system. And that can make it incredibly difficult to make changes, or even to understand which changes will actually matter. That might be overwhelming, but there's hope. Understanding how systems work and how to improve them is something that can be…
To kick off 2025 we're looking at Fyrox a game engine built in Rust, largely by one person - Dmitry Stepanov. For an individual project, it's covered an incredible amount of ground, covering the rendering and animation features you'd expect from a game engine, with some features that might surprise you - like Rust scripting support with hot-reloading. As we dive into Fyrox, Dmitry explains what it takes to build a game engine, why he chose Rust (and why he's happy with the choice), and how one person can hope to build a project of that size. – Support Developer Voices on Patreon:…
About Developer Voices
Deep-dive discussions with the smartest developers we know, explaining what they're working on, how they're trying to move the industry forward, and what we can learn from them. You might find the solution to your next architectural headache, pick up a new programming language, or just hear some good war stories from the frontline of technology. Join your host Kris Jenkins as we try to figure out what tomorrow's computing will look like the best way we know how - by listening directly to the developers' voices.
Developer Voices is a English tech & science podcast from Kris Jenkins. Melo plays each episode straight from the publisher's own feed — no ads added, no account needed — and remembers where you stopped, in this browser only.
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