Episode Details

Brex runs on Elixir. Klarna runs on Erlang. Mastercard is believed to use it. And most of the community that builds on these systems watches them with PromEx - a library written by today's guest.

Alex Koutmos has been in the Elixir ecosystem for over a decade. He wrote PromEx - the Prometheus metrics library most of this audience runs in production - and he's just written Elixir for Finance with his brother Dimitrios, a tenured finance professor at Texas A&M. The book takes Livebook, Explorer, NX, and Scholar and points them straight at markets, trading strategies, and blockchain infrastructure.

Topics include:

• why switching money and routing a stock order are the same problem as switching a phone call - and why the BEAM was built for both

• the ISO 8583 protocol story: 100 lines of C per message frame, dropped to 10 in pure Erlang, dropped to 4 with the bit syntax - and why nobody talks about this

• Explorer as an Elixir wrapper around Polars (a Rust data frame library) - why the BEAM delegates the heavy compute and keeps the orchestration

• how to use Livebook, NX, and Scholar to backtest a moving average crossover trading strategy without leaving Elixir

• why "let it crash" doesn't mean "let the money vanish" - and exactly how a ledger, Oban, and durable event storage keep the truth safe across process restarts

• the difference between a ledger and a database - and why a bank built on plain Postgres misses the point

• blockchain as a distributed ledger: the same distributed state problem the BEAM community was chewing on long before Bitcoin existed

• why fintech companies use Erlang and Elixir as a competitive advantage - and tell nobody

• BlockScout, Aeternity, and where BEAM languages already run in blockchain infrastructure

• what the Python and JVM financial tooling stacks miss that Explorer and NX cover - and where they still win

Recorded August/September 2026.

Resources mentioned:

• Elixir for Finance - the book

• PromEx on Hex

• BlockScout - open source Ethereum explorer written in Elixir

• Aeternity - blockchain built in Erlang