Fork This Conference

Last weekend Heart of Clojure took place in Leuven, Belgium. As one of the core organizers it was extremely gratifying to see this event come to life. We started with a vision of a particular type of event we wanted to create, and I feel like we delivered on all fronts.

For an impression of what it was like you can check out Malwine’s comic summary, or Manuel’s blog post.

It seems people had a good time, and a lot of people are already asking about the next edition. However we don’t intend to make this a yearly recurring conference. We might be back in two years, maybe with another Heart of Clojure, maybe with something else. We need to think about that.

But I do hope the legacy of Heart of Clojure can live on. One of the things we optimized for was socializing, making connections. We brought people from 31 (!) countries together, and enabled countless new connections. This will without a doubt have an impact on the Clojure community.

One of my goals with Heart of Clojure was also to provide people with new ideas. We had a very wide range of talks, many of them not directly related to Clojure, but all of them inspiring and sparking interesting conversation.

Finally I wanted to inspire other conference organizers. I have visited countless technical conferences over the years, and have developed strong opinions about what I think makes an event great. Some of these ideas are already wide spread, some of them are well accepted in other communities, but not yet prevalent in Clojure. In particular I was hoping to introduce some ideas from Ruby conferences like Eurucamp and Isle of Ruby into the Clojure community.

So that’s what this post is about, a quick recap of the specific things we did, that we would love to see others copy. Maybe the existing conferences will pick up a thing or two, or maybe someone else will feel inspired to create a new event. Seems there’s a market for a European summer conference, maybe you want to fill that gap?

A Two Phase CFP

This is already well known by now, but still worth mentioning. Our selection process occured in two steps. First we had a group of reviewers rate talks anonymously. They did not see the speaker’s name or other identifiable details, they just had the title and the abstract. This way you get a largely unbiased rating of the proposal itself.

Once all proposals are rated the program committee made a final selection. This time they did look at who the speakers were, to assure we had a balanced and diverse program, including first time speakers, and speakers from different places geographically, with a strong European representation, since we wanted to also showcase our local talent.

Finally also worth mentioning that after this final selection we paired all speakers up with a mentor. Some people worked together with their mentor extensively, others only checked in once or twice, but the offer was there, to make sure people are supported in delivering the best talk they could.

This is not the final word on finding a good CFP process, I heard that for ClojuTRE Metosin is experimenting with rating talks on multiple criteria, and then making a shotgun spread so you get talks across the spectrum. Hopefully they will write about their experience, and maybe even open source the app they developed for this.

To run our CFP we forked the CFP App developed for RubyConf.

Long breaks

We had 16 sessions spread over two days. That’s not that many, for comparison, the upcoming ClojuTRE has well over 20, which I’d say is fairly typical.

However we made the choice to keep the program fairly light. The sessions are what bring the people together, they provide inspiration and a shared experience, but in my mind a conference is really about meeting people, so we wanted to optimize for that.

We also wanted to prevent (to some extent) the mental exhaustion that easily sets in after a day of listening to talks. So we had plenty of breaks, typically half an hour each, with a one and a half hour lunch break the first day, and an extended lunch+siesta break on the second day.

This siesta break concept was pioneered by Eurucamp, and it took a little bit of convincing to get everyone on the team on board with it, but it’s so great, and people loved it. Basically on Saturday from noon to four people could do whatever. We offered lunch of course, and there were some activities to opt-in to (more on that later), but really it was “space intentionally left blank”. And so people grab a drink, sit on the grass, have long extended conversations. They go back to their hotel to freshen up or take a nap, they head into town, visit a museum, or pull out their laptops to share what they are working on.

The result: a much more interactive event, with deeper, more genuine connections. Trust me, four o’clock is there before you know it.


All these people travel to a country and city they’ve never been to, that has so much to offer, only to sit in a hall and stare at a screen until they’re exhausted. Isn’t that a shame? We wanted people to interact, to explore the city, to do things in small groups, which are so much more amenable to getting to know people.

So we organized Activities. We had guided city tours the day before, we did a creative code jam during the siesta break, there was a screen printing company on site where you could go to get our logo printed or create your own designs.

And other people could create activities as well. Juxt organized an impromptu workshop about Crux, people went bouldering, we had competing beer and wine tasting events, and over a dozen people learned from our sketchnoter Malwine how to sketchnote.

On Friday evening one of our speakers and Leuven native Maarten Truyens organized an “adventurous dinner”. Everyone who signed up got split into twelve groups of six to eight people each, and we made twelve different restaurant reservations, so people could get a dinner with a small group, and meet some of the other attendees, sponsors, and speakers.

Compare this with what usually happens: everyone stands around at the end of the day, clustering into ever bigger groups, and by the time you start moving you realize you need to on the spot find a place that will fit 20 people without prior notice.

To make this all possible we used the activities app first developed for Eurucamp, we just had to style it a bit, and promote it.

Lightning talks

This has always been one of my favorite parts of Ruby conferences. To qualify as a lightning talk a few requirements need to be met. The talks are exactly five minutes each, after five minutes the audience starts clapping and its over, and people sign up for them on the spot, by simply writing their name and talk title down on a big sheet that’s hung up in the venue.

If you like to have everything under control this may seem scary. There’s no telling what people will bring to the stage, but that’s what makes them so great. You get really spontaneous, diverse, and entertaining talks most of the time. And if it’s not, then in five minutes there’s already the next one.

This format allows people to show something they hacked together the day before, or to respond to a talk that they saw earlier at the conference. It allows people who feel a bit insecure to make a last minute call. It’s just a really great format, and I’ve rarely seen it gone wrong. Just make sure everyone is well aware of the code of conduct!

Also worth mentioning is that we did not end the day with lightning talks, which is fairly common. Instead we kept a closing keynote to close off the day and the event. This way you don’t end on the erratic, chaotic energy of the lightning talk session.

We also made sure this closing keynote wasn’t a deep technical talk. I’ve seen a few Clojure conferences do this, and I find it really hard to still engage with at the end of the day, my brain is just too fried. Instead we had a talk about community, focusing on the human aspects, which I thought was a great takeaway to end the day.

Start the second day a little later

Conferences bring far away friends together, and so what do they do after a day of focusing on talks? They go and relax, get a bite, grab a drink, and before you know it it’s two in the morning and you’re calculating how much sleep you can still get and if you’ll skip the first talk or not.

This isn’t necessarily what we recommend people to do, we did mention in a few places to be careful with Belgian beers, and to try and be fresh and bright in the morning (or to at least keep the partying until the end of the second day), but this is still the reality for a good part of the attendees.

So we start a little later the second day (and don’t start too soon in any case). The first day we had doors at 9:00, and started the sessions at 9:30, on Saturday doors opened at 9:45, and sessions started at 10:15. I’ve been to conferences where the first speaker on the second day is talking to just a handful of people, that’s not a fun place to be.


These weren’t the only things that made Heart of Clojure great, some things are harder to copy, and sometimes you have to get a little lucky. I think our biggest strength was the awesome venue, and we were lucky to find it, but it’s also our biggest weakness. If it had been a heat wave like the weak before, or if we had had serious thunderstorms, we would have been in trouble. We were also very close on capacity, there is no room to grow for us at this location.

We were also really lucky with the accessibility, being close to the train station and to Brussels airport, and to be in a city that’s compact and walkable. These are all circumstances that might be hard to replicate elsewhere.

And a final caveat: these things I listed here may not be the right thing for your event. You need to be the judge of that. Different people like different things, and different organizers set different priorities. But hopefully one or two of these ideas can trickle into some of the other great conferences we already have.

And if you do feel inspired to organize a new Clojure conference, once or repeating, then get in touch. We would be really happy to help. Maybe next summer?