To Brussels, Canada and back

Last year was my first year blogging, speaking at conferences, meeting incredible people, and seeing places I’ve never been before. It was at times quite arduous but at the same time energizing, as you can read in my post Looking back on one year of speaking and blogging. I didn’t want it to be a one-off year, so I dutifully started a new blog series on eBPF and applied for conferences… And I got accepted at a few of them, which was really great because I started missing traveling after almost three months of being home. In this blog post, I’ll cover my first three conferences this year: FOSDEM in Brussels, ConFoo in Montreal, and Voxxed Days Zurich; they all happened between early February and early March.

It was the most travel, distance (and continent) wise, that I ever did before, by quite some margin:

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Looking back on one year of speaking and blogging

2023 has been an adventurous year for me: I came into my blogging rhythm, blogging every one to two weeks, resulting in 39 blog posts, spoke at my first conferences, around 14 overall, 22 if you include JUGs and online conferences, and continued working on my IntelliJ plugin, as well as my proposal for a new profiling API. This blog post is a recollection of the year’s highlights. If you want a complete list of my presentations, visit my Talks page or the Presentations page in the SapMachine Wiki.

Before this year, I only gave a few presentations at my local hacker conference, Gulaschprogrammiernacht, and two at local user groups. But then, at the end of December 2022, Abby Bangser asked me whether I wanted to give a talk at QCon London 2023. She apparently noticed me because I started blogging on performance topics, which only a few people do. This resulted in my first proper conference talk with the title “Is Your Java Application Slow? Check out These Open-Source Profilers” and my InfoQ article Unleash the Power of Open Source Java Profilers: Comparing VisualVM, JMC, and async-profiler. I gave a version of this talk at almost every conference I attended.

QCon London was a great experience, albeit I traveled via TGV and Eurostar on my birthday. It was only the second time that I’d been to London, so it was great to explore the city (and have my first blog post, Writing a Profiler in 240 Lines of Pure Java, on the top of the hacker news front page), visiting the British Museum and walking along the Themes:

But this wasn’t actually my first conference talk if you include my two 15-minute talks at FOSDEM 2023 in February, one of which was based on my work on Firefox Profiler:

FOSDEM is an open-source conference where a lot of different open-source communities meet:

The best thing about FOSDEM was meeting all the lovely FooJay people at the FooJay dinner, many of whom I met again at countless other conferences, like JavaZone in September:

In a bar with my fellow speakers

But more on Oslo later. Speaking at QCon London and FOSDEM was frightening, but I learned a lot in the process, so I started submitting my talks to a few conferences and user groups, resulting in my first Tour d’Europe in May/June this year:

I originally just wanted to give a talk at the JUG Milano while I was there any way on holiday with two friends. Sadly, the vacation fell through due to medical reasons, but Mario Fusco offered me a stay at his place in beautiful Gorgonzola/Milan so I could visit Milan and give my talk:

It was where I gave my first presentation in Italy. It was the first time I’ve ever been to Italy, but I hope to return with a new talk next year.

After my stop in Italy, I spoke at a meet-up in Munich, a small conference in the Netherlands, and gave three new talks at two small conferences in Karlsruhe. All in all, I gave eight talks in around two weeks. You can read more about this endeavor in my Report of my small Tour d’Europe. This was quite exhausting, so I only gave a single talk at a user group until September. But I met someone at one of the Karlsruhe conferences who told me at a dinner a month later that I should look into a new topic…

In the meantime, I used August to go on a sailing vacation in Croatia (couch sailing with Zelimir Cernelicc) and had a great time despite some rumblings regarding my JEP:

Before the vacation, I carelessly applied to a few conferences in the fall, including JavaZone in Oslo and Devoxx Belgium. Still, I would have never dreamed of being a speaker at both in my first year as a proper speaker. Being at JavaZone in September, followed by two smaller conferences in northern Germany, was excellent, especially with all the gorgeous food and getting my first duke:

You can read more on this journey in my Report of my trip to JavaZone and northern Germany.

Then, in October, I went to Devoxx Belgium, meeting people like Alexsey Shipilev

Fixing a bug with Alexsey at Devoxx Belgium; see my article JDWP, onthrow and a mysterious error

and eating lunch with four of the Java architects, including Brian Goetz and Alan Bateman:

Giving a talk at such a well-known conference was a real highlight of my year:

You can see a recording here:

After Devoxx, I gave my newly created talk on Debugger internals in JUG Darmstadt and JUG Karlsruhe. This is the main talk I’ll be presenting, hopefully at conferences in 2024.

After these two JUGs, I went to Basel to give a talk at Basel One. After five conferences, two user groups, and eight blog posts, I needed a break, so I went on vacation to Bratislava, visiting a good friend there and hiking together for two days in the Tatra mountains:

Then, at the beginning of November, I gave a talk at J-Fall in the Netherlands, the biggest one-day conference in Europe:

While there, I stayed with Ties van de Ven, a speaker I first met at FOSDEM. At my first conferences, I knew no other speaker; later speaker dinners felt more like reunions:

At the speakers’ dinner at J-Fall with Simon Martinelli and Tim te Beek

While I was giving presentations and writing about Java profilers and debuggers, I also wrote a five-part series on creating a Python debugger called Let’s create a debugger together, which culminated in my first presentation at my local Python Meet-Up:

I went this year from being a frightened first-time speaker who knows nobody to somebody who traveled Europe to speak at conferences and meet-ups, both large and small, while also regularly blogging and exploring new topics. I had the opportunity to meet countless other speakers, including Marit van Dyjk and Theresa Mammerella, who helped me get better at what I do. I hope I can give something back to the community next year, helping other first-time speakers succeed.

To conclude, here is a list of my most notable blog posts:

Next year will become interesting. My first conference will be the free online Java Developer Days on Jan 17th by WeAreDevelopers, where I will give a presentation about debugging. I got accepted at FOSDEM with a talk on Python’s new monitoring API, ConFoo in Canada, JavaLand, the largest German Java conference, and Voxxed Days Zürich, and I hope for many more. But also regarding blogging: I will start a new series soon on eBPF in which we’ll explore eBPF with Java, developing a new library along the way.

I’m so grateful to my SapMachine team at SAP, which supports me in all my endeavors. Be sure to check out our website to get the best OpenJDK distribution.

Thanks for reading my blog; I hope you’ll come to one of my talks next year, write a comment, and spread the word.

This article is part of my work in the SapMachine team at SAP, making profiling and debugging easier for everyone.

Report of my trip to JavaZone and northern Germany

Between 2nd and 17th September, I gave three talks in three different cities:

I traveled from Karlsruhe to Oslo (via Stuttgart Airport) and from Oslo to Hanover via plane, then to Hamburg, Hanover, back to Hamburg, and the end via Bonn back to Karlsruhe via train:

This was my first time traveling to a conference by plane because traveling to Oslo by train takes far longer (20 hours or more).

This was my second two-week-long tour giving talks, after my tour d’Europe in May/June this year (see Report of my small Tour d’Europe), but this time it consisted solely of talks at conferences. The following is a short report of my trip that saw me brewing beer, giving a talk at one of my favorite conferences, and visiting Hamburg for the first time.


I started by traveling to Oslo on Saturday before the conference, which began on Tuesday with workshops. My journey started with the 2:30 am bus from Karlsruhe to Stuttgart, where I took the 6:30 am flight to Paris and from there to Oslo. Flying in the early hours of the morning is something extraordinary:

I’ve never really been to Oslo before, except as a toddler, according to my parents, so I wanted to explore the city. I arrived in Oslo Saturday afternoon and stayed till Tuesday morning at the home of a friendly expat that I met via the couch-surfing platform, staying there till Tuesday morning. It was great: I had the opportunity to visit the famous Fram Polar Exploration Museum, hike around the Vettakollen, and brew beer with my host:


Then, on Tuesday, it was time for the workshop day of JavaZone. I’ve been drawn to this conference since I got introduced to their conference trailers in my first semester at university:

So, speaking, there was a great honor; I can recommend this experience to anyone. It is a lovely venue with good food and great organizers who care about their speakers (shout out to Felix Rabe, Rafael Winterhalter, and Marek Machnik).

I started the conference by attending the “A little taste of testing the Java compiler” workshop by Hasnae Rehioui:

Hasnae Rehioui, in her workshop

If you want to start with building the OpenJDK and running JTREG tests, her accompanying website is an excellent place to start.

At the end of the day, I went to the speaker dinner, where I met the organizers and people like Fabian Stäber and Gunnar Morling. The view from the restaurant was majestic:

Then, the next day, the conference began. The conference paid for the hotel during the week. I met Pasha Finkelshtein and Marit van Dijk from JetBrains at the breakfast buffet. I was that day in many talks, including the Maven Puzzlers talk by Andres Almiray and Ixchel Ruiz:

The day ended with eating with a few of my fellow speakers and going to the AweZone party at Himkok bar, but only after a musical performance by Mr. Orkester:

What a great way to inform all JavaZone participants of the looming AweZone event.

The next day was full of talks, including mine and eating great food. I now understand why some people call JavaZone affectionately FoodZone, with all the food served all day. My talk was in the first slot at 9:00 am; I was amazed that around 150 people turned up to attend it after the long night at the bar:

Thank you to Inna Belyantseva for the great Math-as-a-Service logo and valuable feedback on my presentation style in the weeks before the conference.

Later in the day, I went to Theresa Mammarella’s talk on CVEs:

I was introduced to her the evening before, and it was great to see the only other young JDK developer (in her case, OpenJ9) on stage.

In the evening, I ate dinner with a couple of my fellow speakers, including Marit van Dijk, Rustam Mehmandarov, Gerrit Grunwald, Raquel Pau, Tim te Beek, Steve Poole, Alina Yurenko, Theresa Mammarella, Mads Opheim and Ko Turk. Afterward, we went to Himkok bar to relax after two days at the conference:

The next day was my last in Oslo before moving to northern Germany. So I took the chance to explore the city center once more and made a photograph of the speaker’s gift:

A Viking duke in front of the Oslo Stock Exchange

I had to say goodbye to Oslo and then traveled to Hamburg via Hanover Airport to stay with a friend in Hamburg.


The problem was that JavaZone pays the hotel till Friday, and the speaker dinner for Java Forum Nord is Monday evening. I knew someone in Hamburg, so I stayed in Hamburg from Friday night till Monday afternoon. I used the time to look into Python debugging, which eventually resulted in my Let’s create a Python Debugger together: Part 1 blog post, went sightseeing, watched the dark comedy Sophia, der Tod und Ich, and visited the Hamburger Miniaturwunderland:

While there, I had the pleasure of traveling with light luggage, as my luggage didn’t arrive in Hamburg till Wednesday because it was somehow stuck in Amsterdam airport, where I had a stopover.

Java Forum Nord

The second conference on my journey was the Java Forum Nord in Hanover on Tuesday. This conference is a small community-run event, without many sponsors and many talks in German. It was my first German Java conference, so there were many German-only speakers that I hadn’t seen at a conference before. I met a few of them at the speaker’s dinner on Monday and at the after-party on Tuesday:

Speakers’ dinner with alcohol-free beer and Spätzle in Hanover

I enjoyed meeting Marit van Dijk again and getting to know Sandra Parsick and Karl Heinz Marbaise.

The day after, I traveled back to Hamburg for the code.talks conference.


This was the third conference in a row and the only one without a focus on Java. The talks were on various technologies, from NFTs to creativity. The most memorable of the conference was by far the speaker’s dinner at the open kitchen restaurant Hensslers Küche and visiting the Heavens Bar & Kitchen rooftop bar in St. Pauli with Jacqueline Franßen, Hannes Drittler, and Samir Ar after the second day of the conference:

While there, I also started preparing an upcoming talk for JCon World with Marit van Dijk and had an online meeting with Jaroslav Bachorik and Erik Österlund on the future of my JEP, so stay tuned.

I traveled back to Karlsruhe via Bonn, where I met a good friend and attended a Haydn concert in the Kreuzkirche, closing the eventful two weeks cooking flammkuchen together with her and one of her new flatmates.


Giving three talks at conferences in a row was an experience I’m grateful for. Talking with many new and old acquaintances was, at times, taxing, yet definitely worthwhile. Especially JavaZone was a conference I never dreamt of being able to speak at.

I’m looking forward to giving many more in the future and happy that the SapMachine team at SAP allows me to do so and fully supports me in my endeavors.

If you want to attend one of my talks, just come to Devoxx Belgium, BaselOne, or J-Fall, where I’ll speak this autumn. You can find all the meet-ups and conferences that I’ve confirmed on my Talks page. I’m happy to talk at your meet-up or conference; just ask me.

This project is part of my work in the SapMachine team at SAP, making profiling easier for everyone.