New BEAM There, Done That with Alex Koutmos, who built PromEx and co-wrote Elixir for Finance with his brother Dimitrios (finance professor at Texas A&M).
The most Erlang-relevant moment in the episode: a bank’s ATM interface runs on ISO 8583, a binary protocol with a bitmap header specifying which fields are present. The original C implementation ran to 100 lines per frame just for parsing. Moved to Erlang: 10 lines. Once bit syntax was applied - matching binary structure directly in the function head - it came down to 3 lines. Francesco frames it directly: the BEAM was built to parse and switch binary protocol messages, and a payment is a binary protocol message.
The episode also covers the broader fintech adoption picture. Brex and Klarna are confirmed Erlang/Elixir users. JP Morgan Chase is believed to be. Companies treat it as a competitive advantage and don’t publicize it - a dynamic Joe Armstrong noted personally when an engineer admitted to using Erlang while their company publicly claimed Java.
BlockScout (open source Ethereum explorer) is written in Elixir. Aeternity is a blockchain built in Erlang with its own VM. The distributed ledger problem - independent nodes that must agree on truth without trusting each other - is a problem the BEAM community was working on long before Bitcoin formalized it.
