Dutch Clojure Days 2026

About DCD 2026

The Annual International Gathering of Clojure Enthusiasts and Practitioners in the Netherlands! We welcome you to the 6th 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.

When?

Dutch Clojure Days is scheduled to happen on .

Where?

Dutch Clojure Days will take place at the amazing City of Wesopa, in the stunning Amsterdam city district of Weesp (Herengracht 23, 1382 AG Weesp).

Tickets

Registrations are open and free of charge. Go ahead and get your ticket now!

Sponsors

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

Partner

Supporter

Sponsorship Packages

Want to join us in spreading the Clojure love? We'd be thrilled to have you as a sponsor! We've got three awesome sponsorship packages designed to fit every budget:



If you want to support and engage with the Dutch Clojure Days community, please get in touch via email at events@clojuredays.org.

Agenda

The agenda below is just an indication as our CfP is still ongoing!

8:30

9:00

Reception

9:00

9:15

Opening#DCD26 team

9:15

10:00

Shapes of TogetherDaniel Slutsky

11:45

12:30

Reevaluating the IDEAdrian Smith

10:45

11:15

Coffee break
Lightning Talks

11:15

11:25

clj-simple-stats: statistics that is actually easy to setup and useNikita Prokopov

11:25

11:35

MilaDB: 0-deps embeddable time-traveling databaseBenny Andresen

11:35

11:45

Unlocking the power of SQLite with coffi (JDK 22 FFI)Anders Murphy

11:45

12:30

Clojure as Your First Language: Shaping a Functional MindsetWendy Randolph

12:30

14:00

Lunch break

14:00

14:45

Sound theory, music theory and analogue synthesis, with OvertoneArne Brasseur

14:45

15:30

Bear's Browser Bet: A ClojureScript StoryRiccardo Cambiassi
Lightning Talks

15:30

15:40

Fun with JVM flagsRay McDermott

15:40

15:50

Bringing async/await from Squint to ClojureScriptMichiel Borkent

15:50

16:00

On growing a communityErik Assum

16:00

16:10

Closing#DCD26 team

Speakers

Daniel Slutsky

Shapes of Together

In this talk, we discuss how spaces for collaboration form and grow, drawing on experiences from local activist groups, from building Scicloj, and from watching newer spaces like Clojure Civitas. Using Clojure's tools for visual storytelling, we'll dive into the stories of these communities and others: their conversations, their activity over time, and how they've changed.
Community building raises questions. How do we create spaces where diverse voices are genuinely heard, yet still find common direction and reach decisions when needed? How do we support people of different backgrounds? How do we maintain continuity when individuals come and go, and what structures serve a group that keeps changing? How do we nurture ideas that challenge mainstream thought, yet remain welcoming to those encountering these ideas for the first time?
In times of uncertainty, we don't have to be alone. With care, building together becomes possible. We'll consider what that care may look like, and ask: what do we still need to build for each other?
About the speaker: Daniel Slutsky is a Clojurian and a mathematician. Since 2019, he has been involved in building Scicloj, an open-source community focused on helping Clojure grow. He co-maintains a few tools and libraries, including Noj, Clay, Tableplot, and ClojisR.

Adrian Smith

Reevaluating the IDE

What would a Lisp IDE with modern graphics, multi-threading, advanced JIT compilation, world class garbage collection, and an enormous ecosystem of libraries look like? What would programming look like if our workflows were oriented around data rather than text? What if it was easy to build and integrate tools dynamically at runtime that were tailored to the specific problem domain?
For the past year, I've been working on Easel, a pure Clojure IDE. In this talk, we'll explore ideas from the past that were ahead of their time, demonstrate what's possible today, and imagine what the future of IDEs could look like.
About the speaker: Adrian is a software engineer and the creator of Easel, a pure clojure IDE in the spirit of Emacs. He got started programming by making tic-tac-toe for his TI-83 calculator. Since then, he's built web, mobile, and desktop applications using python, javascript, ruby, php, objective-c, and c++ before finally finding clojure. He believes that programming should be for everyone and that you shouldn't need a CS degree to make a simple web, desktop, or mobile app.

Nikita Prokopov

lightning talkclj-simple-stats: statistics that is actually easy to setup and use

Brief overview of clj-simple-stats: a website statistics middleware for Ring servers that requires no configuration, can be plugged in with 1 line of code and Just Works™
About the speaker: Nikita has been programming in Clojure, Java, Python, Erlang for 19 years, been interested in UI/UX design for about the same amount of time, and created a few notable projects, including DataScript, Rum, Clojure Sublimed, Tongue, Clj-reload, Uberjars, Clj-simple-router, Humble UI and Fira Code.

Benny Andresen

lightning talkMilaDB: 0-deps embeddable time-traveling database

A Database heavily inspired by Datomic and its descendants like Datascript, Datahike, Datalevin and most recently dbval.
The value proposition is: db-as-a-value, running in process, zero dependencies, backed by bbolt's simplified-from LMDB database design.
Wherever you would use SQLite and you're into Datomic-flavored Datalog, MilaDB could be an option.
About the speaker: Benny is a Clojure developer in Northern Germany. Not the best place to spend lots of time in the hammock, but he makes it work.

Anders Murphy

lightning talkUnlocking the power of SQLite with coffi (JDK 22 FFI)

In this session I'll cover how the coffi library lets you use JDK 22 FFI to make C bindings. This unlocks bindings in C libraries that are often not implemented in high level wrappers. In the case of SQLite there's a whole suit of powerful features that are hard to access from more generic database wrappers like JDBC.
Coffi's macros and memory arenas make programming C from Clojure fun.
About the speaker: 👋 Hi! I'm Anders. A Fullstack Developer, Product Engineer and Startup Founder from Edinburgh (UK). I've spent most of my career building consumer facing apps.
I do consulting work on: Clojure, JVM, SQLite, product design, rapid prototyping and performance tuning (with a focus on vertical scaling).
Currently I'm working for Lightweight Labs.

Wendy Randolph

Clojure as Your First Language: Shaping a Functional Mindset

What happens when your first programming language is Clojure? Are we all born with an inherent fear of parentheses? How does immersing yourself in its powerful abstractions shape your problem-solving approach? In this talk, I’ll share how Clojure, as my first language, shaped my mindset and set me on a path to becoming a more flexible, creative, and precise problem solver. We’ll explore how Clojure’s minimalist syntax and focus on immutability, recursion, and purity build a solid foundation in functional programming. Discover how the REPL’s feedback loop accelerates learning and encourages experimentation. Clojure’s simplicity fosters good habits early on, helping avoid unnecessary complexity and preparing you for modern software challenges, especially in scalable and distributed systems. Learn how this Lisp dialect nurtures a functional mindset, setting you up to excel no matter the language you work with.
About the speaker: Wendy is a career-changer and freelance software developer, passionate about functional programming and helping others break into tech. A founding student of Clojure Camp, she has spoken at numerous conferences, such as Clojure Conj, Heart of Clojure, Lambda Days, Clojure South, and Lambda World, co-hosted ElixirConf US and Clojure Conj 2025, and enjoys sewing, jazz dance, sports cars, and Disney.

Arne Brasseur

Sound theory, music theory and analogue synthesis, with Overtone

With Overtone Clojure has one of the coolest live music coding environments in existence, but the learning curve is steep. Overtone has fewer built-in instruments than for instance Sonic-Pi, assuming that people will be more interested in building their own synths and instruments instead. As a result the biggest barrier to entry often isn't really about Clojure or Overtone, but about sound, music, and the principles of analogue synthesisers.
In this very hands-on talk I want to present some basic sound and music theory, and then go over the most common synthesis techniques, like additive synthesis, subtractive synthesis, frequency modulation, etc. Showing through live examples in Overtone how much fun can be had, and encouraging people to start exploring this wonderful world themselves.
About the speaker: Arne is the CEO and founder of Gaiwan, the company behind Lambda Island and Heart of Clojure. He teaches and consults about all things Clojure and ClojureScript, as well working tirelessly to improve the Clojure ecosystem through open source software like Kaocha, and community initiatives like ClojureVerse.

Riccardo Cambiassi

Bear's Browser Bet: A ClojureScript Story

In 2017, I presented a talk at Dutch Clojure Days about shipping ClojureScript apps. This is what happened next.
Bear is an award-winning note-taking app for the Apple ecosystem, loved by users worldwide. We brought it to the web using ClojureScript and Re-frame - with no backend, syncing directly with Apple's CloudKit from the browser.
After several years of development, here's what we learned:
  • Re-frame patterns that survived the test of time
  • wrapping JS interop with CloudKit: the undocumented parts
  • integrating with WebAssembly from ClojureScript
  • Offline-first sync and conflict resolution
  • What worked great and what didn't
  • Where ClojureScript saved us time and how the landscape evolved around us
  • What's next: from CRDTs and embedded SQLite

This is a production story from someone who bet on ClojureScript years ago - and would do it
About the speaker: Managing Director and Tech Lead at 100Starlings, a remote-first software develoment agency. He has been designing and building web applications for the best part of three decades.

Ray McDermott

lightning talkFun with JVM flags

A small comic interlude on how the JVM flags can be reinterpreted for fun and no profit
About the speaker: Clojure enthusiast, podcast host. Seasoned, veteran, perhaps even a classic, old fart or haha a senior developer

Michiel Borkent

lightning talkBringing async/await from Squint to ClojureScript

In this talk you will learn how I ported Squint’s implementation of async/await to ClojureScript and how you can use it to simplify asynchronous code.
Three years ago I presented Squint at Dutch Clojure Days: a dialect of ClojureScript that supports modern JavaScript (ES6) features such as async/await. Async/await allows asynchronous code to be written in a sequential style. The `await` keyword marks a point where execution pauses until a result is available, without blocking the runtime. When the result arrives, execution continues where it left off.
Since then, porting it to ClojureScript itself has been on the back of my mind. The main obstacle was that ClojureScript historically targeted older versions of JavaScript and was deliberately conservative about adopting newer language features. Now, a decade after ES6 was introduced, ClojureScript targets ES6 as its baseline. This shift has renewed interest in integrating features such as async/await directly into ClojureScript.
The talk covers the design constraints, compiler changes, and trade-offs involved in bringing async/await semantics to ClojureScript.
About the speaker: Michiel Borkent, known online as @borkdude, is a passionate open source Clojure developer. He’s helping developers to write cleaner, faster, and more enjoyable code with popular tools like clj-kondo, babashka, SCI, nbb, and squint. When he’s not deep in parentheses, you’ll find him at the piano or enjoying a walk outdoors.

Erik Assum

lightning talkOn growing a community

The Clojure community is a small one. Perhaps you live in a place where the scene is not yet vibrant and thriving. In this lightning talk, I'll give a couple of tips on how to get your local community going with very low effort
About the speaker: Erik is a wearer of many hats at Ardoq, a Norwegian scale up in the enterprise architecture space . He’s a mainly a backend programmer, but tends to work wherever the code is bad enough. Given time he’ll eventually drift into some sort of devops role while trying to figure out how to run the current project even better.
Lately, he's been lurking around open-source Clojure projects looking for easy bugs to fix. This is his way of paying back to the community.

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.