After ten years keeping Klarna's payments alive, he wrote the BEAM book
Why I wrote the BEAM book (2025)
The author spent over a decade running Klarna's core system on the BEAM, where a 15-millisecond pause could stall millions of peak-shopping payments. He started the book in 2012, survived two cancelled publishing deals, and finally shipped a paperback in 2025. It covers schedulers, process memory, garbage collection, tagging schemes, the compiler, tracing, and performance tuning — the manual he wished he'd had when things went wrong.
Two cancelled publishing deals look bad on a résumé, but an unfinished idea looks worse.
- ErikStenman
The second edition is out now.
- dimamik
I've been building with Elixir for the last 5 years, and comparing to Python or NodeJS - it's a breath of fresh air. Such decent developer experience, so easy to understand how your system works because of actors and well-defined primitives. If you haven't - you definitely should give it a try!
In an AI era I feel like the tiny amount of Elixir code in comparison with other languages, but all that code having higher signal to noise ration vastly contributed to how good LLM-written Elixir code is. Especially in a well-maintainted codebase that relies on a decent db schema and Oban.
- neya
Oh wow, I never knew Klarna uses BEAM. I always thought BEAM is vastly underrated and it's even hard for me to convince clients of showing how powerful it (Elixir/BEAM) really is, especially when they're already on something like NodeJS. This will be a nice reference to use in conversations with future prospects.
- pjm331
just picked up a copy
I'd been looking for an excuse to build something in Elixir pretty much since the language was released, and in just the past year and a half I've had the good fortune of getting to use it to build an in house AI agent orchestration system and it's been an absolute pleasure
- oivaksef
There will be winners in this new AI age, and they will be the ones that are technically better, rather than the most popular or convenient for software engineers