Dutch Clojure Days 2019

About DCD '19

The Annual International Gathering of Clojure Enthusiasts and Practitioners in the Netherlands!

We welcome you to the 4th edition of our free and non-profit Clojure conference organised by the community, for the community with a full day of amazing talks in a friendly welcoming atmosphere. Reserve your free spot today!


Dutch Clojure Days will happen on Saturday April 6th, 2019.


DCD is a free event that is made possible thanks to our amazing sponsors and volunteers.


Bozhidar Batsov

nREPL Redux

After years of stagnation nREPL left Clojure Contrib and its development has resumed! It wasn’t easy, it took a lot of work, I learned many valuable lessons along the way, and I want to share all of this with you! This talk is going to examine the efforts that lead to restarting the active nREPL development in 2018, the current state of the project and the ambitious plans for its future. As almost all Clojure developers rely on nREPL in one way or another (e.g. cider-jack-in or lein repl), I believe that many of you might find this talk both interesting and informative! A maybe even fun! ;-)
About the speaker: Bozhidar is the maintainer of CIDER, nREPL and many Clojure libraries related to Clojure tooling. He’s also the editor of the community Clojure style guide. Most people would probably describe him as an Emacs zealot (and they would be right). He’s also quite fond of the Lisp family of languages, functional programming in general and Clojure in particular. Believe it or not, Bozhidar has hobbies and interests outside the realm of computers, but we won’t bore with those here.

Bahadir Cambel

Building BNR Smart Radio & FD.nl Recommender system using Clojure & Serverless Architecture

Managing servers and infrastructure is a costly, time consuming huge pain. This talk is going to demonstrate how Clojure is a perfect match for Serverless Architecture and how to max AWS capabilities to build your ultra-scale system without any frameworks.
About the speaker: Software Architect & Lead Data Engineer @fd_nieuws #Clojure #Python distributed computing. Runner. Almost ultra-marathoner Freelancing for FD & Schiphol Runs more than he should.

Rakhim Davletkaliyev

Decentralized evolutionary computation with Clojure and ClojureScript

Let’s get inspired by biological evolution and write a decentralized genetic algorithms framework entirely in Clojure and Cljs. Then let’s use it to casually tackle some NP-complete problems by combining the computing power of all devices of Clojure Day 2019 participants!
About the speaker: Software developer since 2010. Co-founder of Hexlet, an educational startup from Finland which is the home of 200k students who learn computer programming and software development, get hired and build cool stuff. In November 2019 resigned as CEO and about to launch something new. I organize free workshops and open lectures on programming and computing in Helsinki. Blog at rakhim.org.

Alex King

How we migrated a complex JavaScript application to ClojureScript step-by-step

As software evolves along with the languages and frameworks it is built upon, it’s easy to create a monster. This is the tale of tackling complexity at the heart of Exoscale, and how a data-driven approach with ClojureScript enabled us to seamlessly replace a JavaScript app without user outage.
About the speaker: Alex King is a software engineer from the UK, currently based in Switzerland with Exoscale. He is passionate about delivering clean, well tested code, that is easy for others to understand. He is well experienced with over 15 years of software development, and adept at bridging the gap between the front-end and back-end teams. He was responsible for large rewrites of core architecture behind the BBC Sport and BBC News platforms, and worked as a consultant for JUXT, where he helped to develop a large Clojure(script) application used by traders at Credit Suisse, along with many years of Scala development before finding a home with Clojure. Away from the day job he can be found enjoying hammock time up in the mountains, or on stage in a dive bar with a guitar in hand.

Heimo Laukkanen

lightning talkClojure powered services at Finnish Broadcasting Company

Finnish Broadcasting Company runs the most loved streaming service in Finland. One enabler is the use of Clojure, which empowers teams to build and operate robust micro-services. This talk shares our experiences and learnings on how we have enabled developer success in our ecosystem since 2015.
About the speaker: .

Ruben Hamers

lightning talkDiscourje: Automatically validated message exchange patterns in Clojure.

The core.async library provides many high-level features for async programming, but does not protect against classical concurrency problems. Discourje extends core.async and offers high-level abstractions to define message exchange patterns that are run-time validated and enforced between threads.
About the speaker: I got in touch with Clojure while reading about Java concurrency and was instantly fascinated by the elegance of Clojure’s syntax and macros. Inspired and enthused by previous research on high-level abstractions for MEPs (e.g., in Java, JavaScript, Rust, and Go), I initiated the Discourje project to bring such abstractions for the first time to Clojure. As a part-time master student at Open Universiteit, I am currently finishing my MSc thesis on Discourje (and its underlying formal theory!). In my full-time day-to-day job, I work as a software engineer at BlueTea (www.bluetea.nl) where we build virtual simulations and serious games.

Michiel Borkent

lightning talkRe-find: discover functions with spec

Re-find is an app and a library that lets you interactively discover Clojure functions based on example in- and output values or predicates. In this talk we will see how it works and how it is implemented, using clojure.spec as the driving force.
About the speaker: Michiel Borkent is a software developer and Clojurian. He can be found as @borkdude in various places on the web.

Matthew Ratzke

lightning talkFuture boot

Boot-clj is a powerful tool for any Clojure developer, find out about the new maintainers, and what we have planned for the future of boot. Here’s a hint: native images.
About the speaker: Matt is a self-proclaimed Clojure Entrepreneur. Using Clojure as a foundation for his startups, matt is currently working on solutions for the Canadian cannabis industry. He is also the lead maintainer of boot-clj and contributes heavily to Hoplon and the boot-clj ecosystem.

Mey Beisaron

How I Supercharged Learning Clojure through Gamification

Gamification can be an excellent way to reduce the barrier of entry & quickly learn new programming languages. This talk will dive into how through a simple game you can master new syntaxes by applying concepts from languages you know & leveraging shared libraries to ramp up your coding skills.
About the speaker: Mey Beisaron is a public speaker, a Clojure, Java, and Node.js developer and a software engineering graduate. When she is not spending her weekends at hackathons, she experiments with algorithms or learns languages such as russian, french and italian. Mey is also a sworn star wars fan. May the force be with you.

Phillip Mates

The rise and fall of e2e testing at scale

Last year I presented on single-service testing. This year I’d like to focus on how Nubank has evolved multi-service testing: our adoption & eventual abandonment of end-to-end tests; the rise of light-weight cross-service generative-based schema validation tests
About the speaker: Coming from a background in theoretical programming language research I’ve been coding Clojure at Nubank for the last 2 years. In this time I’ve become the maintainer of Midje, co-authored a library for validating nested data-structures that produces readable diffs (matcher-combinators), and participated in projects to scale Nubank’s testing infrastructure past 100 microservices. I’m currently focused on building data infrastructure out of Nubank’s small Berlin office.

Joël Kuiper

Starting a new project is always hard. The blank pages stare at you. Sometimes you know what needs to be done, but sometimes the requirements are totally unknown. Three years ago Doctor Evidence decided to build a biomedical search engine, and this talk will be about our journey into the unknown.
About the speaker: I once set out on doing academic research for a living, but then thought better of it. Received a Bachelor of Science degree in Artificial Intelligence from the University of Groningen, the Netherlands. I’m passionate about software development, user experience, and machine learning. Hobby astronomer by night.


Dutch Clojure Days took place at the wonderful TQ, in the heart of Amsterdam (Singel 542, 1017 AZ Amsterdam).

Reserve your Spot

DCD 2019 will be in Amsterdam on Saturday on April 6th, 2019! We are sold out - sorry!

Call for Proposals

Our CFP is now closed.

Code of Conduct

All attendees, speakers, sponsors and volunteers at our conference are required to agree with the following code of conduct. Organisers will enforce this code throughout the event. We expect cooperation from all participants to help ensure a safe environment for everybody.

Need Help?

You can always reach out to us at events@clojuredays.org or on twitter.

The Quick Version

Our conference is dedicated to providing a harassment-free conference experience for everyone, regardless of gender, gender identity and expression, age, sexual orientation, disability, physical appearance, body size, race, ethnicity, religion (or lack thereof), or technology choices. We do not tolerate harassment of conference participants in any form. Sexual language and imagery is not appropriate for any conference venue, including talks, workshops, parties, Twitter and other online media. Conference participants violating these rules may be sanctioned or expelled from the conference without a refund at the discretion of the conference organisers.

The Less Quick Version

Harassment includes offensive verbal comments related to gender, gender identity and expression, age, sexual orientation, disability, physical appearance, body size, race, ethnicity, religion, technology choices, sexual images in public spaces, deliberate intimidation, stalking, following, harassing photography or recording, sustained disruption of talks or other events, inappropriate physical contact, and unwelcome sexual attention.

Participants asked to stop any harassing behavior are expected to comply immediately.

Sponsors are also subject to the anti-harassment policy. In particular, sponsors should not use sexualised images, activities, or other material. Booth staff (including volunteers) should not use sexualised clothing/uniforms/costumes, or otherwise create a sexualised environment.

If a participant engages in harassing behavior, the conference organisers may take any action they deem appropriate, including warning the offender or expulsion from the conference with no refund.

If you are being harassed, notice that someone else is being harassed, or have any other concerns, please contact a member of conference staff immediately. Conference staff can be identified as they'll be wearing branded clothing and/or badges.

Conference staff will be happy to help participants contact hotel/venue security or local law enforcement, provide escorts, or otherwise assist those experiencing harassment to feel safe for the duration of the conference. We value your attendance.

We expect participants to follow these rules at conference and workshop venues and conference-related social events.