Sebastian Seilund Sebastian Seilund

About me

Sebastian Seilund

I'm Sebastian Seilund, a freelance software developer from Copenhagen, Denmark. I live in San Francisco. My big passion is software development and my business.

Also check out my work to read more about what I do.

Software interests

I guess I'm a fullstack developer. I've always been involved in both the back-end and the front-end. I've implemented countless systems by myself doing everything from spec writing, architecture, programming, server setup and deployment.

My favorite programming language these days is Elixir. Functional programming has really started to resonate with me. It resolves a lot of gripes I've always had with other programming languages. I dig the Erlang process model. The popular Phoenix framework is truly a breeze to work with and the pure speed of it is astounding.

I've also done a ton of Node.js since 2012. It's the programming language we have the most services in production with at Billy.

I've worked on advanced JavaScript webapps since 2007. Today I'm a big Ember.js enthusiast. I love the community behind Ember and the smart people working on it. The thing I like about Ember is that you can keep applying the same pattern over and over again to a growing app and it never gets out of control or becomes unmanageble. It scales. I've also toyed around with React and Mithril.

Before 2012 I worked mostly with PHP. I've also had occasional experiences with programming languages such as Ruby and Python, and in University I got some Java, C and C# coding in.

I've grown fond of working with event sourcing and CQRS. It provides elegant solutions to a lot of problems that I've encountered in the past with basic (No)SQL databases, where you only read exactly what you write. My favorite event storage database is Event Store.

I honestly also enjoy DevOps. I like smooth procedures for as many things as possible, and building tools often helps me achieve just that. In a small company, however, it's important to focus on getting stuff done, too.


During my career I've been very fortunate to be nominated/awarded for various acomplishments:

  • 2016: 1 of 5 finalist for "CTO Hero Of The Year" at Nordic Startup Awards.
  • 2014: Selected as "Talent 100" by Danish business media Berlingske Business, which is a list of 100 young talents with future leadership potential, for my work with Billy. I was in the "Entrepreneurs" category.
  • 2008: On the team that won "Best Newcomer" at the Danish E-Commerce Awards.


I was born in Copenhagen, Denmark, in 1988 and grew up there. In 2012 I moved to San Francisco, where I lived for 3.5 years. In 2015 I moved back to Copenhagen for a year. Now I'm back in San Francisco.


I'm a self-taught software developer. I started learning to program around the year 2000. In 2008 I enrolled in the BSc. in Software Development program at the IT University of Copenhagen. At that time I had already been working professionally with software for several years, but I learned a lot of important software skills that I wouldn't want to be without today. I put my bachelor on hold in 2011 to focus on the launch of Billy, and have never had a chance to get back. And at this point I probably never will.