Cowboy is a small, fast, modular HTTP server written in Erlang.
Express is a web application framework for Node.js, released as free and open-source software under the MIT License. It is designed for building web applications and APIs.
Facebook pixel is an analytics tool that allows you to measure the effectiveness of your advertising.
Heroku is a cloud platform as a service (PaaS) supporting several programming languages.
reCAPTCHA is a free service from Google that helps protect websites from spam and abuse.