BEAM There, Done That

Plangora

BEAM There, Done That is a podcast about building real systems with Elixir, Erlang, and the BEAM.

We’ve built it before — distributed systems, fault‑tolerant services, event pipelines, real‑time apps, production nightmares, and the supervision trees that saved them.

Each episode dives into practical lessons from shipping software on the BEAM: architecture decisions, scaling challenges, operational failures, and the patterns that actually work.

No hype. No theory without scars. Just hard‑won experience from engineers who’ve been there.

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27 episodes
weekly
Avg 56 min
English

Episodes 27

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S1 · E30
Friday · 1 hr 9 min
Kip Cole on Time, Localization and Building Agenda
The Navajo Nation inside Arizona observes daylight saving. The Hopi reservation inside the Navajo Nation skips it again. There's a corner of the Yucatan Peninsula that takes 20 minutes to drive through and costs you an hour on your sat nav. No compiler warns you about any of this. Kip Cole has spent 10 years building the Elixir libraries that handle what software gets wrong about human reality: localization, time, and scheduling. CLDR/ex_cldr gave the ecosystem 173,000 Unicode characters and locale-aware formatting for numbers, dates, currencies, and units. Tempo remodelled time as an interval instead of an instant. And this week, Agenda shipped - the scheduling engine four years in the making. Topics include: why localization is not translation - the three things that go wrong in an e-commerce search before a single word has been mistranslated the 10-year weekend project: how a localization library for Elixir turned into 28 packages and a full rewrite into Localized why compile-time code generation with Elixir macros hit a wall - 1,000+ function clauses and quadratic compile times - and why moving to runtime fixed it the astronomical algorithms scar: three years of learning a new branch of mathematics to implement calendar software the BEAM was never designed for what Tempo makes explicit that everyone does by accident: time as an interval, not an instant why scheduling is just set intersection over everyone's free and busy intervals - and why that single insight collapses almost every hard scheduling problem how "sometime on Tuesday" is not a time but a domain error - and what Tempo forces you to say instead Unicode version 18, 173,000 human language characters, and why most language ecosystems still can't represent them correctly the difference between CLDR (the Unicode standard) and Localized (the Elixir implementation of it) what Agenda actually ships this week and what's next Recorded September 8th, 2026.
S1 · E29
September 18 · 1 hr 11 min
Is Your Elixir Code Actually Fast? Tobias Pfeiffer on Benchmarking
Everyone has an opinion about whether the BEAM is fast or slow. Almost nobody has actually measured it properly. Tobias Pfeiffer -PragTob on the internet, benchmarking nerd, real-time engineer at Supabase -came to Elixir from Ruby because Ruby couldn't handle WebSockets at scale. Then he learned the language the way he learns every language: by building a benchmarking library. Ten years later, Benchee is what most of the Erlang and Elixir world reaches for when it wants a number instead of an argument. Topics include: why Tobias writes a benchmarking library every time he learns a new language -and what that discipline actually teaches about how a runtime works the production scar: a benchmark that showed one query was faster, deployed it, and discovered the benchmark had been measuring the wrong input entirely the single most important insight about benchmarking: most people quietly fool themselves and walk away more confident and more wrong than when they started inputs as a first-class feature -the lesson José Valim taught Tobias within 17 minutes of an open GitHub issue why body-recursive map is faster than tail-recursive map for small lists on the BEAM -and what that tells you about the runtime what reductions are, why they're a more stable measurement than wall time, and when they diverge how Benchee measures memory: spawning a monitored process, watching GC events, reporting exact bytes -and why deterministic code gives deterministic memory the JSON benchmarking arms race -built-in OTP JSON, jason, Jiffy, and why comparison benchmarks usually miss the point why Benchee has no macros, no DSL, and deliberately only uses functions -and why that design decision made it composable in ways nobody predicted the hardest benchmarking mistake to stop making: confusing latency and throughput what Toby wishes more Elixir developers understood about BEAM performance before they opened a PR claiming something was faster Recorded August 21, 2026. Resources mentioned: Benchee on Hex: hex.pm/packages/benchee Benchee HTML formatter -self-contained HTML output with downloadable graphs Benchee markdown formatter PragTob on GitHub: github.com/bencheeorg
S1 · E28
September 11 · 1 hr 11 min
Louis Pilfold on Building Gleam - Static Types on the BEAM
What if the BEAM had a language that felt like talking to a friend instead of fighting a compiler? That's the problem Louis Pilfold set out to solve. He loved the BEAM. He missed static types. Every other option was a tradeoff he couldn't live with. So he built Gleam - and after years of quietly saying no to everything he wasn't sure about, it's gathered a community, found production users, and now runs on servers, browsers, and $2 microcontrollers. Topics include: why every successful language is born from a problem - and what specific frustration made Louis start building rather than just complaining the discipline of saying no: no if, no currying, no pretending two targets are one world the design decision Louis regrets most - the conditional compilation syntax he's now stuck with and desperately doesn't want more people to use why Gleam's concurrency model lives in a library rather than the language - and what that buys in terms of flexibility when smarter people eventually improve it how Gleam solved the problem everyone said was unsolvable: "you can't type message passing on the BEAM" what the JavaScript and BEAM targets share and where they genuinely can't be unified - and why pretending they can leads to terrible architecture why Gleam chose Erlang records as its data structure and what that costs at runtime Lustre, Gleam's web framework - beating mainstream JavaScript frameworks in benchmarks while written entirely in Gleam how Louis funds his work on Gleam: GitHub Sponsors, the Gleam community, and what sustainable open source actually looks like from the inside what Gleam will look like in 3–5 years - native records, better JavaScript interop, and why the language's approach to stability makes those changes possible Recorded August 20, 2026. Resources mentioned: gleam.run - docs, tour, community tour.gleam.run - interactive language tour running the Gleam compiler compiled to Wasm, takes an afternoon Exercism Gleam track Code Crafters - build Redis/SQLite/Git in Gleam GitHub Sponsors: lpil (Louis Pilfold) Lustre - Gleam's web framework
S1 · E27
September 4 · 36 min
How WhatsApp Fixed Erlang's Tooling Problem | Roberto Aloi & Michał Muskała
Part one established that Erlang scales. Part two is about what comes after - keeping a codebase that large healthy for years, when most engineers arrive having never written Erlang before. WhatsApp's answer was to invest in the language itself. The formatter, the language server, the type checker. And then to open source almost all of it back to the community - not as charity, but because diverse use cases and external bug reports make the tools better. Roberto Aloi and Michał Muskała are back for the half that doesn't appear on conference posters. Topics include: why the investment in tooling came from a developer survey rather than an engineering instinct - the data showed Erlang developer experience was the weak point what ELP (the Erlang Language Platform) actually is and how it superseded the Erlang LS that Roberto built before joining WhatsApp how eqWAlizer, WhatsApp's type checker, was rolled out without breaking other teams - the team owning the type checker also owned the task of fixing things up when new checks introduced errors why types and let it crash aren't in tension: you can never statically verify everything in a dynamic language, so the gap is where supervision and recovery fit the two biggest misconceptions about static analysis tools: that they're slow (modern tooling is fast) and that you have to commit to them all at once (you can do it incrementally) why WhatsApp open sources tools that took significant engineering investment - keeping them internal would make them worse, not better what's still unsolved: exhaustiveness checks at this scale remain an open problem how AI is changing the Erlang learning experience - build first, ask AI to review your patterns afterward the word that ties both episodes together: trust. Supervision earns it at runtime. Types earn it at compile time. Companion episode: Part 1 on scale and operations. Recorded June 25, 2026.
S1 · E26
August 28 · 34 min
Inside WhatsApp with Roberto Aloi & Michał Muskała
Everyone quotes WhatsApp when the topic of Erlang and scale comes up. Fewer people know what it actually looks like from the inside - what was hard, what was never hard, and what the team spent their time on once the concurrency stopped being the problem. Roberto Aloi and Michał Muskała work on the team keeping it running. This is the first of two episodes with them. Topics include: what Roberto's first Erlang moment was - implementing a GenServer for a robot at university and learning binary pattern matching felt like cheating why Michał came to Erlang backwards, from Elixir, and what the tooling gap actually felt like the column numbers OTP bug that caused cascading failures and taught Roberto what no documentation could the optimization that made the JSON Unicode parser slower - binary pattern matching was the wrong tool, and a custom state machine was faster what "let it crash" actually means at WhatsApp scale: letting it crash is the easy part, recovery is where the engineering lives why the 30th employee was the first person at WhatsApp with Erlang experience - and what that means for hiring the most misunderstood thing about Erlang at WhatsApp: scaling isn't the exotic part, keeping the codebase healthy is how WhatsApp does deployments: 1% of servers first, one region next, monitoring throughout, ready to roll back what types of failures become normal at this scale - and why disaster recovery drills are a regular practice overly dynamic code as the anti-pattern that creates the most sustained pain Part two covers ELP, Equalizer, and the tooling that keeps a codebase this large navigable. You want both. Recorded June 25, 2026.
S1 · E25
August 21 · 54 min
Erlang on a Microcontroller: Davide Bettio & Paul Guyot on AtomVM
In 1952, Marvin Minsky and Claude Shannon built a box with a single switch. When you flip it, the only thing it does is reach out and switch itself back off. Seventy years later, 5,000 of those boxes are sitting on desks worldwide — and the thing making them tick is Erlang, running on a chip smaller than a fingernail. Davide Bettio built AtomVM, the virtual machine that makes this possible. Paul Guyot wrote the Erlang firmware, added SMP support as a weekend project, and shipped 5,000 units. Topics include: what AtomVM is — a from-scratch BEAM-compatible VM for microcontrollers with a few hundred kilobytes of RAM and no OS debugging a virtual machine with no stack traces: printf everywhere, blindfolded the first production batch with a 5–10% return rate that turned out to be a mechanical problem — after Paul rewrote half the software looking for a bug that wasn't there why the actor model, let it crash, and binary pattern matching are unusually well-suited to embedded devices what AtomVM actually supports: GenServer, maps, JSON, Erlang distribution, and via the Popcorn project — Phoenix LiveView on a microcontroller Paul's SMP implementation as a "mixed blessing" — added for purely selfish engineering reasons, then forced the whole team to rewrite their drivers where AtomVM differs from the BEAM: no dirty schedulers, no hot code unloading, a simpler scheduler model that mostly doesn't surface at the API level Recorded June 24, 2026. Resources mentioned: atomvm.net GitHub: atomvm/AtomVM Popcorn project — Phoenix LiveView on AtomVM Discord: AtomVM community
S1 · E24
August 14 · 1 hr 19 min
Mat Trudel on Building Bandit - the Web Server Running Your Phoenix App
Bandit quietly became the default web server in Phoenix. Mat Trudel wrote it by hand, in pure Elixir, as a side project - and kept it that way even as AI changed how everyone else writes code. This episode goes two places at once: the engineering of a foundational piece of infrastructure most developers never think about, and an honest conversation about what it means to keep building something by hand when you don't have to. Topics include: how a six-month debugging session - Wireshark, a 30-page RFC, and a single misread line in the HPACK spec - explains why HTTP is genuinely hard to get right what "one process per connection" actually buys you at 3am when something's on fire: a stack trace that's entirely Elixir frames, all the way up why HTTP parsers have a million attack vectors that have nothing to do with which language you write them in the WebSock and WebSock Adapter split - and why a web server depending on another web server is ridiculous how José Valim looked at Mat's first WebSocket implementation and told him he was doing too much an AI-generated PR sitting open on the Bandit repo that implements the entire HTTP/3 stack - and why Mat hasn't merged it why Mat still writes Bandit entirely by hand while using agents for everything in his day job the cabinet maker's son analogy that explains the whole thing: if you want cabinets, go to IKEA; if you want to build them, the journey is the point what it means when "finding bugs got cheap but judging and fixing them didn't" Companion episode: Peter Ulrich and Jonathan Machin on CVEs and security - the same story from the reporting side. Recorded June 22, 2026. Bandit quietly became the default web server in Phoenix. Mat Trudel wrote it by hand, in pure Elixir, as a side project - and kept it that way even as AI changed how everyone else writes code. This episode goes two places at once: the engineering of a foundational piece of infrastructure most developers never think about, and an honest conversation about what it means to keep building something by hand when you don't have to. Topics include: how a six-month debugging session - Wireshark, a 30-page RFC, and a single misread line in the HPACK spec - explains why HTTP is genuinely hard to get right what "one process per connection" actually buys you at 3am when something's on fire: a stack trace that's entirely Elixir frames, all the way up why HTTP parsers have a million attack vectors that have nothing to do with which language you write them in the WebSock and WebSock Adapter split - and why a web server depending on another web server is ridiculous how José Valim looked at Mat's first WebSocket implementation and told him he was doing too much an AI-generated PR sitting open on the Bandit repo that implements the entire HTTP/3 stack - and why Mat hasn't merged it why Mat still writes Bandit entirely by hand while using agents for everything in his day job the cabinet maker's son analogy that explains the whole thing: if you want cabinets, go to IKEA; if you want to build them, the journey is the point what it means when "finding bugs got cheap but judging and fixing them didn't" Companion episode: Peter Ulrich and Jonathan Machin on CVEs and security - the same story from the reporting side. Recorded June 22, 2026.
S1 · E23
August 7 · 1 hr 3 min
Erlang Without an OS: Maxim Kharchenko on Building LING
Booting OTP without a Linux kernel underneath it. Running Erlang directly on a Xen hypervisor. Implementing a VM where every single out-of-memory condition is explicitly handled — not a single allocation without a recovery path. Maxim Kharchenko spent five to eight years building Ling, a from-scratch Erlang runtime that runs without an operating system. Not a fork of the BEAM. Not a modification. A clean implementation, built to answer one question: can you run a system that never stops? Francesco Cesarini joins Alan Wyma for this episode — he was there when it was built, running the Erlang Solutions team that worked on the other half of the project. Topics include: how Maxim came to Erlang backwards — building his own isolation-based runtime first, then discovering Erlang had already solved the same problems what a Xen hypervisor actually is and why it's the right host for a no-OS Erlang VM how Ling's dynamic instruction set works: analyzing real OTP source code to figure out the optimal instruction set for that specific workload, then generating specialized opcodes — including one that loads the number 17 specifically because 17 appeared frequently enough to warrant it why every single memory allocation in Ling has an explicit out-of-memory handler — and how hard that discipline was to maintain the garbage collector design for bare-metal network applications and why it matters differently there than in regular BEAM workloads running the entire network as an Erlang application: not just a piece of it, but switch firmware, controller, and the full stack why the industry was not ready for this ten years ago — and why the problems Ling was solving have come back under different names where unikernels and Linux eBPF fit in the same space today Recorded June 3, 2026.
S1 · E22
July 31 · 42 min
Mike Williams & Björn Gustavsson on Building the JAM
Before the BEAM, there was the JAM - Joe's Abstract Machine. It was the first virtual machine that made Erlang fast enough to run in production, and it was built by a handful of people at Ericsson's computer science lab who had a mandate to do whatever they wanted. Mike Williams wrote large parts of the emulator. Björn Gustavsson inherited it in 1996 and built what came after. In this episode - the most historically significant we've recorded - Alan Wyma and Francesco Cesarini bring them both together to tell the story of where the BEAM actually came from. Topics include: why Mike looked at Joe Armstrong's first 20 lines of C and said "this is awful, I'll do something about it" - and how he got message passing down to six instructions the three numbers that decide whether a concurrent language lives or dies: process creation time, context switch time, and message copy time - and why 70% of VM time was spent on them, not application code why keeping concurrency inside the language rather than the OS was "perfectly obvious" to Mike, and why it was a minority view even then - Java removed green threads, early Rust removed lightweight processes the two-version rule for module hot loading that's still in the BEAM today, 30 years on - and why Björn never wanted to remove it memory as the binding constraint, not speed: phone switches handling whole cities ran on 16–64 MB of RAM how distribution was added to the JAM by Claes Wikström - the person whose name is always forgotten in this story, who also invented ETS tables and created the first prototype of Erlang's binary syntax what Björn saw when he first read Mike's code in 1996, why he liked the JAM more than the BEAM at first, and what finally made the JAM obsolete the computer science lab culture that made Erlang possible: no publish-or-perish pressure, just a mandate to solve a real problem Recorded June 4, 2026. Resources mentioned: "History of Programming Languages" paper, Joe Armstrong (HOPL III) Bjarne Däcker's licentiate thesis Early Erlang CS lab technical reports (ERN series)
S1 · E21
July 24 · 45 min
Elixir in the Browser: Bart Blast on Hologram
What if instead of making your server smarter to handle the browser, you just ran your Elixir in the browser instead? That's the bet Bart Blast has been making for six years - three of them full time. Hologram is a full-stack web framework that compiles Elixir to JavaScript and rebuilds the Erlang runtime in the browser: pattern matching engine, OTP guarantees, boxed types, all of it. No JavaScript to write. No round trip on every interaction. No inconsistent state between client and server. This is the fourth episode in the podcast's ongoing series on where state should live - following Chris McCord on durable servers, Adi Iyengar on building a web framework, and Brooklyn Zelenka and Robert Virding on local-first. Bart made the opposite bet to Live View. Topics include: why Bart spent six years building this instead of reaching for existing tools - and why the answer is "plain frustration" the latency ceiling you can't engineer past on the server, and why bandwidth improvements don't help how Hologram actually works: pulling the expanded AST from compiled BEAM files, normalizing it, lowering to an IR, and encoding to a JS runtime - including a real pattern matching engine and boxed types why Hologram doesn't merge front end and back end - there's still a clear separation, just one language crossing it actions vs. commands: the two behavior primitives and which side of the client/server boundary each lives on where Live View wins over Hologram - and Bart is honest about this (private logic, data-heavy apps, maturity) how Hologram compares to Luster (Gleam's equivalent) and why neither is competing with the other when you should not use Hologram yet where it's all heading: local-first sync layer, mobile, desktop, and eventually a single Elixir codebase for everything Recorded June 18, 2026. Resources mentioned: hologram.page hologram.page/newsletter GitHub: barb/hologram Discord: hologram community Hologram tag on Elixir Forum Website: https://hologram.page GitHub: https://github.com/bartblast/hologram Newsletter: https://hologram.page/newsletter Discord: https://discord.com/invite/huJWNuqt8J Elixir Forum: https://elixirforum.com/hologram X: https://x.com/Bart_Blast LinkedIn: https://www.linkedin.com/in/bartblast/ Bluesky: https://bsky.app/profile/bartblast.com Slack: https://elixir-lang.slack.com/channels/hologram
S1 · E20
July 17 · 1 hr 2 min
Zig Meets the BEAM: Garrison Hinson-Hasty & Isaac Yonemoto on Safer Native Code
Everyone who's ever written a C NIF for the BEAM knows the story. You have a bottleneck, you reach for native code, it works - until one day it doesn't, and instead of a process crashing, the whole node goes down. A segfault in a NIF takes the entire BEAM with it, bypassing every fault-tolerance guarantee OTP was designed to provide. This episode asks a simple question: do we have to accept that? The answer, increasingly, is no. Allen Wyma and Francesco Cesarini sit down with Garrison Hinson-Hasty, author of Systems Programming with Zig, and Isaac Yonemoto, creator of Zigler - the library that lets you write Zig directly inside Elixir and Erlang modules, with automatic marshalling, scheduler-aware execution modes, and memory tracking that's visible to the BEAM itself. This is part of the podcast's ongoing "right tool for the job" series, following earlier episodes on Rust and native code. Topics include: what Zig is and why it exists - C's simplicity and zero-cost abstractions, without C's footguns how Zig compares to both C and Rust: where it wins, where it loses, and why they're solving different problems why Zig's allocator model is unusually well-suited for BEAM integration - and what it means that Zigler uses the BEAM's own allocator by default, making native memory visible to Erlang's VM how Zigler works: write Zig in a sigil inside your Elixir module, and the marshalling between BEAM terms and native types is handled automatically at function call boundaries the four execution modes Zigler gives you - normal, dirty CPU, dirty IO, spawned thread - and how to pick one without changing a single line of your Zig code the honest answer to the question every BEAM developer wants to ask: can a Zigler NIF still crash the whole node? (Yes. Isaac explains exactly when and why, and what Zig's spatial memory safety actually buys you) why Zig has no hidden control flow and no lexical macros, and why that matters when you're debugging something at the boundary between two runtimes where Zig's async story currently stands, and what that means for Zigler's roadmap Isaac's unusual professional position: CEO of a pharma startup who is also writing the software stack for his own lab in Zig and Elixir Recorded June 9, 2026. Resources mentioned: Systems Programming with Zig by Garrison Hinson-Hasty Zigler on Hex and GitHub Zigler docs
S1 · E19
July 10 · 1 hr 1 min
Inside the BEAM JIT: How Lukas Backström Made Erlang Faster
In 2021, Erlang got something it had been promised for years: a Just-In-Time compiler. The person who built the first working prototype, spent years on failed experiments before it, and quietly shipped it to every Erlang and Elixir system on the planet is Lukas Backström — OTP team member since 2009, Francesco Cesarini's former student, and one of the most consequential engineers in the ecosystem that most people have never heard of. In this episode, Alan Wyma and Francesco Cesarini sit down with Lucas for a deep dive into how the BEAM JIT actually works, what it took to get there, and where it's heading next. Topics include: the difference between interpreter, ahead-of-time compilation, and JIT — and why the BEAM's threaded code interpreter was already unusually fast why tracing JITs — the first several approaches Lucas's team tried — worked great on microbenchmarks but failed on real Erlang code, which is highly branchy and unpredictable the key insight that killed LLVM: faster code generation with AsmJIT was worth more than LLVM's optimizations, once you account for startup time how the template JIT design — copy-pasting assembly from templates into memory, then specializing a few bits — became the architecture that shipped why WhatsApp was running the JIT from the tip of master the day it was released, nine months before the official OTP 24 tag how type-guided optimizations now flow from the Erlang compiler into the JIT — and why a simple integer add can now compile to a single assembly instruction the Apple M1 announcement that changed the release timeline and forced ARM64 support a year ahead of schedule what's actually left to do: smarter code loading, better startup time, and the native records implementation touching every layer of the system why the BEAM JIT is one of the simpler JITs you could read — and how to inspect the assembly it generates for your own code Recorded May 27, 2026.
S1 · E18
July 3 · 1 hr 3 min
Static Types Finally Come to the BEAM | Annette Bieniusa & Guillaume Duboc
Joe Armstrong once said anyone can write a type system covering 90% of Erlang — it's the remaining 10% that defeats even the brightest minds in computer science. He was referring to Philip Wadler. That was 1995. Thirty years later, the BEAM is finally converging on an answer. In this episode, Alan Wyma and Francesco Cesarini sit down with Annette Bieniusa, professor of software technology at RPTU Germany, and Guillaume Dubois, PhD from IRIF Paris now at Dashbit, to dig into what it actually takes to bring static types to Erlang and Elixir — and why it took this long. Topics include: why every serious attempt at typing Erlang since 1995 — soft types, subtyping, Dialyzer — ran into the same wall, and what's genuinely different now what set-theoretic types are and why they're the foundation Elixir 1.2's type system is built on how Elixir's gradual type system differs fundamentally from TypeScript or Python's approach — and why baking dynamic in from the start changes everything why the BEAM ran telecoms for 25 years without static types, and what problems types are now actually solving the risk nobody talks about: developers getting lulled into false confidence by type checking, writing fewer supervision trees and less defensive code how Annette's parallel etalizer for Erlang and Guillaume's Elixir work share the same theoretical foundation but make different design choices why "type systems don't mean error-free" — and what types actually buy you on the BEAM specifically what Elixir 1.2 ships, what's still being worked on, and the one thing you can do this week Recorded May 28, 2026.
S1 · E17
June 26 · 53 min
30 Years Inside the BEAM: Björn Gustafsson on Building Erlang's Runtime
Three engineers. Three different virtual machines. One conversation that started with the JAM and ends with the JIT compiler. Allen Wyma and Francesco Cesarini sit down again with Björn Gustafsson — member of the OTP team since 1996, and the person who has personally shepherded the BEAM through every major transition since taking it over from Bogdan Wódzicki — for a deep dive into 30 years of runtime engineering. Topics include: the three competing virtual machines built in parallel at Ericsson's lab — JAM, Robert Virding's V, and Bogdan's BEAM — and why each one's design choices succeeded or failed a compiler bug that caused random crashes and took weeks to find — and the BEAM Validator that was built specifically so it could never happen again why "turbo Erlang" compiled-to-C delivered a 10-20x sequential speedup on paper that shrank to 2x once concurrency entered the picture, and why that mattered for chip design the BEAM loader — Björn's own invention, still in use today — and why decoupling the compiler from hand-written runtime translation mattered how Björn took over Bogdan's code in 1997 and turned a research prototype into a 30-year production runtime without ever breaking backward compatibility what's coming next: the JIT compiler (next episode), type systems, and a possible episode on the historical and emerging Erlang machines -record(history, { jam, v, turbo_erlang, beam }). If you care about language runtimes, VM design, or how production systems survive three decades of evolution without ever stopping, this episode is for you. Recorded May 26, 2026.
S1 · E16
June 19 · 40 min
Why Elixir Beat Go and Rust for BlueSky's Data Plane | Chris Beck
There's a gap between BlueSky's open reference implementation (handles a few hundred thousand users) and BlueSky's own production system (handles millions, but runs on infrastructure most teams can't replicate). Chris Beck and his team at Bitcrowd set out to close it -and ended up somewhere they didn't expect. In this episode, Allen Wyma and Francesco Cesarini talk to Chris Beck, founder of Bitcrowd in Berlin, about building an open source alternative to BlueSky's data plane -the component that turns the AT Protocol firehose into the timeline you actually scroll through. This is the third episode in our "right tool for the job" series, following Rust and Zig. Topics include: what the AT Protocol actually is, and why it's closer to an "operating system for social apps" than a single product why BlueSky's own production solution (similar to Discord's MongoDB → Cassandra → ScyllaDB journey) is out of reach for smaller communities the real numbers: 200-500 messages/second on a normal day, 6 million active users during the November 2024 US election the hot path vs. cold path split that shaped the entire architecture why Go, Rust, and Node were all evaluated and rejected -including why Node's single-threaded event loop was already a dead end for the BlueSky team themselves why Elixir wasn't the expected choice, and what ETS gave them for free that they'd have had to hand-build everywhere else using a Rust NIF via Rustler for roaring bitmaps to solve the "social proof" (mutual follows) feature -and what that NIF actually costs in terms of crash isolation why losing almost every microbenchmark didn't matter once they asked "do we actually need to go there?" the fan-out architecture that pushes messages directly into user mailboxes, and why that made backpressure a non-issue what's left to build, and the one sentence Chris wants every team picking a stack to remember Recorded June 15, 2026.
S1 · E15
June 12 · 1 hr 6 min
Why Multiplayer Games Are Just Distributed Systems | Ellyse Cedeno on BEAM & the Actor Model
Every player is a process. Every monster is a process. Every zone is a process. Sound familiar? In this episode, Allen Wyma and Francesco Cesarini sit down with Ellyse Cedeno - technology and product leader with 25+ years across online games, distributed systems, and real-time platforms - to explore why the BEAM and the actor model are a natural fit for multiplayer game servers, and why the games industry keeps learning this the hard way. Topics include: why MMORPGs and telecom systems have more in common than most people realize the N-squared problem: why high player density is so expensive and how classic games solved it why Java threads and deadlocks were the original game server nightmare how the actor model eliminates lock management - and what that means for mob AI event-sourced vs tick-based architecture and when each makes sense zones, sharding, and the air traffic control analogy for seamless server handoffs building a NetHack-style multiplayer game in LiveView - and what the DOM diffing taught her about game state why the games industry is dominated by C++ and Unreal, and what it would take to change that using player behavior analytics to catch bugs before ops teams or server logs do the production horror story of someone pulling the live database drive mid-operation Plus: why Ellyse wants to publish a 100% Elixir game on Steam, and what the open source game_server project on Codeberg is trying to do. Recorded May 25, 2026.
S1 · E14
June 5 · 1 hr 6 min
Who Builds the Next Generation of Senior Devs? Bruce Tate on AI, Juniors, and the Career Path Crisis
The dashboards are green. PRs are shipping faster than ever. So why are seniors quietly burning out — and juniors not actually learning? In this episode, Allen Wyma and Francesco Cesarini sit down in person with Bruce Tate — author of Seven Languages in Seven Weeks, co-author of 10+ books on Elixir, and founder of Groxio — who just shut down a 10-year mentoring organization because the junior developer career path had become too unclear to sustain. Topics include: why AI has broken the traditional apprenticeship model without replacing it three scenes from a Tuesday afternoon: Freddie the junior, Martin the senior, and the manager watching the green dashboard — what each is missing about the other two the five modes of AI-assisted coding (completion, mini tasks, debugging, collaboration, vibing) and which ones a junior should actually live in why the pull request is no longer a learning moment — and what to do instead the four things a junior must develop to become a senior in 2026 what leadership owes the next generation, and the one pledge every team should make where BEAM languages fit in all of this — and why Elixir may be the best language for AI-assisted development The productivity dividend is real. The question is whether we invest it or eat it. Resources mentioned: Groxio: grox.io Tidewave Ash Framework "Tell Me a Story" talk by Sasha (referenced in episode) Recorded May 18, 2026.
S1 · E13
May 29 · 1 hr 2 min
AI Found 5 CVEs in One Afternoon — The BEAM Security Wake-Up Call | Peter Ullrich & Jonathan Machen
The BEAM ecosystem spent decades flying under the radar - too niche to attract serious attackers. That era is over. In this episode, we sit down with Peter Ullrich, the developer who ran a $10 experiment at ElixirConf EU in Málaga and discovered a vulnerability that could crash the BEAM with a 13-character string - with zero prior security experience. Then we hear from Jonathan Machen, CISO of the Erlang Ecosystem Foundation, whose job is to catch and coordinate everything Peter finds. We cover: How Peter built a simple bash script that scanned the most-downloaded Hex packages - and what he found Why LLMs have changed the cost and skill floor for vulnerability research forever The CVE disclosure process: what happens from the moment a bug is found to the moment it's published How the EEF's CNA went from 9 CVEs in a year to more in a single week What library maintainers should do right now (spoiler: it's three clicks on GitHub) The AGES initiative, supply chain security, and the gap between what's been built and what the moment demands Why paying a vendor like Trivy isn't enough - and what actually needs to happen If you run Phoenix in production, this episode is required listening. Resources mentioned: Peter's blog post and prompts: github.com/pultrich (linked in post) Linux Foundation's Scrutineer project Report vulnerabilities: cna@erlef.org Support the Erlang Ecosystem Foundation: erlef.org
S1 · E12
May 22 · 54 min
Inside the BEAM: Björn Gustavsson on Maps, Records, and Runtime Design
For the first time in over a decade, the Erlang runtime is gaining a new native data type — and on this episode of BEAM There, Done That, hosts Francesco Cesarini and Allan Wyma sit down with Björn Gustavsson, known by many as the “B” in BEAM. Björn takes listeners deep into the history of records, maps, tag bits, and the architectural trade-offs that shaped the Erlang runtime from the 1990s to today. The discussion explores why records were originally implemented as a hack, why maps never fully replaced them, and what finally made native records possible after nearly 30 years. Along the way, the episode becomes a rare tour through BEAM internals, compiler design, runtime tagging, and the practical realities of evolving a production VM used at massive scale. If you care about language design, runtime systems, or the history and future of Erlang/OTP, this is one of the deepest technical conversations the podcast has released.
S1 · E11
May 15 · 1 hr 1 min
Inside Phoenix: A Plug, a Macro, and What You Need to Know To Build Your Own Framework
Three and a half years, one book, and a clearer answer to what Phoenix is actually doing under the hood. Phoenix makes building web apps in Elixir feel effortless, but how much of that is genuine elegance and how much is metaprogramming hiding the complexity? Adi Iyengar spent three and a half years writing Build Your Own Web Framework in Elixir to find out, and in this episode he sits down with Francesco and Allen to share what he learned by rebuilding Phoenix from the ground up. We dig into Plug as the real heart of the framework, when metaprogramming is the right tool and when it quietly becomes a liability, and why understanding the layers underneath Phoenix is what separates a productive developer from a senior one. Along the way Francesco brings out the BEAM web-server history most listeners have never heard — Yaws, Bluetail, Mochiweb, Inets — and the conversation lands on what coding agents get wrong about Phoenix in 2026.

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