Dennis Tel


I enjoy building high quality products with a focus on usability, maintainability and simplicity — in both implementation and design.

My Toolkit of Choice

Design & Development
Elixir logo


My go-to language. Its simple, flexible and makes concurrent solutions — like real-time interfaces — easy to build. It's REPL provides a fast feedback loop that helps build solutions fast and makes it a joy to work with.

Typescript logo


When working on frontend applications my language of choice is TypeScript — for now. It provides access to the vast JavaScript ecosystem while at the same time help make JavaScript's idiosyncrasies more manageable through it's typesystem.

Ruby logo


The first programming language I learned and still the one I find the most wonderful to write. For any scripting or simple data processing Ruby remains my go-to.

Kotlin logo


A mostly Object-Oriented language but highly influenced by functional languages like Scala, Erlang and ML which help with some of the shortcomings of Object Oriented programming. It's a swiss army knife and sometimes feels like Ruby, which makes it a pleasure to work with.

Clojure logo


What attracts me the most to Clojure are the philosophy of the language and the ideas that come from its community. Its challenging the way you think about programming which leads you to create simpler and more sophisticated solutions. It can also run in many different environments like the JVM, JavaScript and .NET which means you can write it pretty much everywhere.

ReasonML logo


The number one language that is most likely to replace TypeScript in my toolkit. It has an extremely nice type system which is sound and gives it the feel of writing a dynamic language, simply because it figures out the types for you. And its compile times put other compile-to-js languages to shame.

Sketch logo


Even though my main focus is on programming, I actually have a background in design. Because of this I can easily work with designers and help translate their ideas to code. For sketching out ideas and designs not a lot comes close to Sketch and its features.

Whimsical logo


For all your the diagramming, flowcharting and mindmapping needs look no further. Whimsical is the tool that gets out of the way and lets you focus on structuring your thoughts instead of fiddling with knobs and dials. Useful regardless if you're a designer or developer.

Some of my writing:

My Career


I'm currently a Fullstack Developer at Aiden, building solutions for clients our homegrown platform that enables companies to give their clients complex financial advice. I also coach the team during the sprints and retrospectives and facilitate an agile culture.

Betty Blocks

Betty Blocks is developing a no-code platform to help non-developers build business applications. I contributed to the migration from Ruby to Elixir and train new developers in Elixir. Another part of my responsibilities were increasing the release frequency of features by streamlining our Git strategy and migrate the platform to Kubernetes on Azure.


At Wakoopa I got my first job out of University. After doing my internship and thesis here, I became responsible for the frontend of its SaaS offering. I collaborated with UX Designers to design and implement single page applications using Ember and React. I also worked on the rest API built with Ruby on Rails. In my final year I worked on an iOS and Android app to help research participants install Wakoopa's software, built with React Native.

Amsterdam: University of Applied Sciences

At the University of Applied Sciences I studied Communication and Multimedia design. The study is focussed on User Experience design, Interaction design and Frontend development. Most of my elective courses where focussed on Interaction design, information architecture and philosophy and ethics. I was a teachers assistent and helped teach HTML, CSS and JavaScript to fellow students.

Graphic Design School of Utrecht

At the Graphic Design School of Utrecht I studied All-round Desktop Publishing. I learned to prepare documents and books for print and which printing techniques to use. I had a few classes in typography and webdesign which influenced the rest of my career path.