Simpli.fi takes part in nearly two million and growing ad auctions per second. Each auction is for only a fraction of a penny; but at this frequency, such fractions can accumulate to tens of thousands of dollars in minutes.
Our real-time accounting system is built with a mixture of Elixir and Erlang. It achieves high throughput while servicing 25,000+ (doubling every 8 months) active ad campaigns worldwide. Our performance can be directly measured in dollar figures in real time. Downtime and inaccuracy are both immediately obvious and costly.
We wrote this application in Erlang and it has been in production for over two years. Today we do all new development in Elixir. I'll discuss the evolution of our approach and how the Erlang VM has proven a great fit for real-time accounting. I'll also talk about how we've revised our design and assumptions over the course of scaling ten-fold.