Sebastian Seilund Sebastian Seilund

My work


I'm a software engineer at Google. I work on Hire - a recruiting app for G Suite. My primary focus is on integrating Hire with the rest of G Suite.


Billy is an online accounting software that I founded in 2010. We made it simple for our users to manage their accounting. Users can send invoices, manage bills, reconcile their bank and much more.

Our Danish beta went online in Denmark in April 2011 and in August 2011 we started accepting customers. In 2017 we had around 10,000 active paying customers in Denmark.

I sold my shares in Billy and left the company as CTO in 2017.

Billy's front-end is a large Ember.js app, which we started working on in the summer of 2012 (when Ember.js was still on v0.9.8). This has brought me an extensive experience with Ember.js and large-scale webapp development in general.

The back-end evolved into a microservice-oriented architecture. We ran about 50 services primarily written in Node.js, a few others in Elixir, Python and PHP. Several new parts of the system use event sourcing and CQRS. All the services run as Docker containers in an AWS cluster managed by Apache Mesos and Marathon. We have a single public REST API that we use for both our own webapp and external applications.


I taught myself programming somewhere around year 2000 and have been hooked ever since.

Before founding Billy I spent most of my time doing consulting for other companies and occasionally some of my own projects, too.

Here are some of the fun projects I've worked on in the past:

  • An ad space auction site.
  • A system that manages bookings for a rental company.
  • An online portal where parents of school kids can order lunch for their children.
  • A system that analyzes live sports data and provides real-time feedback to users.
  • Countless webshops.
  • An ERP system for a company that sends weekly newsletters to paying subscribers.
  • A photo-sharing service.