Spring I/O is something I discovered on YouTube a few years ago and have been a fan of ever since. I used to watch each and every published video and stay amazed by the quality and the general sense of community. Year after year I looked forward to seeing those familiar faces. I could recognize almost all of them by name and domain, and slowly this feeling of familiarity was born.
This year I decided to invest in this event and attend it in person (supported and almost forced by Tornike). It was not a small decision, since I had to cover a lot of it out of my own pocket, but it was worth it.
Here are some highlights, conversations, and impressions from the conference that I just could not keep to myself, right?
April 13, Community Night
The conference kicked off with a community night gathering at a local bar. We enjoyed some drinks and had warm conversations in the unofficial setting. This really helped break the ice and bring people together. I would highly recommend attending these kinds of icebreaker events if you ever get a chance. Who knows, you might even say hi to those you look up to.
On that night I finally met people in person from Switzerland, Germany, Austria, Lithuania, Norway, and many more. I had a great time discussing AI, humanity, and the future of both (because who can avoid that at a tech conference?). These people stayed as anchors for me throughout the whole conference, helping me navigate the situation and enjoy my time there.
April 14, Day 1 of Spring I/O
The conference venue was beautiful and well-chosen, with a huge garden around it.
The interior was well-designed and comfortable, with huge halls that created a sense of freedom and creativity and naturally encouraged conversations.
Started the day with coffee and reunited with some of the colleagues from the previous night.
The opening ceremony included a performance of Rosalia’s Berghain (spot-on in Barcelona), and the host, Sanderson Jones, never let us feel bored.
After that, the serious part (but still fun) started.
Josh Long’s Bootiful Spring Boot 4 was exactly the kind of session you expect from Josh: high energy, a little chaotic, and never boring. I especially liked seeing API versioning, resilience additions like @Retryable and @ConcurrencyLimit, and a stronger security story without everything feeling heavier because of it.
The broader Spring AI Ecosystem in 2026 talk made one thing very clear: calling an LLM is the easy part now. The actual work starts afterwards, with memory, validation, tools, context management, and all the orchestration needed to make the thing behave. And Spring AI is getting increasingly ready for the challenges.
Patrick Baumgartner’s From chaos to cohesion was one of the talks that hit a nerve for me. Anything that says “maybe do not rush into microservices and pay distributed tax for no reason” already has my attention, and the vertical-slicing angle made a lot of sense.
The Koog + Spring AI + Spring Boot session by Vadim Briliantov was one of the most memorable for me. The human-physiology analogy alone was enough to make it stick: backend as the body, Spring AI as the nerves, Koog as the brain, persistence as the immune system, observability as the mouth, history compression as sleep. Strange? Yes. Effective? Also yes. Really rooting for Koog.
And Simon Martinelli’s Spec-driven development was a good reminder that AI does not save us from having to think. It can speed things up, sure, but weak requirements plus fast generation still equals chaos. I greatly recommend having a look at his spec-driven, iterative methodology called AI Unified Process.
So overall, the first full conference day gave me exactly what I had hoped for: practical ideas, familiar names, and a lot of stuff to think about and improve next time I sit down with my projects.
April 15, Day 2 of Spring I/O
Not bragging at all, but this was a special day as I took part in the community run event organized by IntelliJ itself (not kidding) - I even got limited running apparel. I was stressed beforehand, fearing that I might embarrass myself and be crawling the whole time (it was 5-6 km, a sweet spot for me, but “easy” by others’ assessments).
We caught the early sunrise, ran through the area around the conference venue, and started the day energized. It was the first time I had run in a group, and my running buddy (we were mostly running in pairs or a few people per line), Mauricio Salatino was a great company, so I barely felt the fatigue. After a quick shower back at the hotel, it was time for more sessions.
Mark Pollack’s From completions to goals workshop continued the same theme from the previous day, but in a much more hands-on way. My main takeaway was very simple: if we cannot evaluate what the agent did and how well it did it, then we are just vibing professionally 🫣.
Thomas Vitale’s Arconia for Spring Boot also caught my attention because it addressed a very specific pain point: repetitive setup, tiny workflow annoyances, and developer friction that slowly drains your will to live. I always respect tools that try to simplifying things instead of making everything even more complicated.
Victor Rentea’s Top 10 event-driven architecture pitfalls was exactly as fun and traumatic (and dramatic and entertaining 😅 It’s Victor, expecting nothing less) as it sounds. Duplicate deliveries, out-of-order events, race conditions, lost messages - all the usual reminders that distributed systems never let us relax for long.
And finally, the observability session by Jonatan Ivanov and Tommy Ludwig was a good reminder that it is not enough for systems to run; we also need to understand what they are doing while they are running. Logs, metrics, traces, health checks - none of this is optional, no matter how much people enjoy treating observability like some sacred art.
By that point, I was tired in the good way: a lot of input, a lot of conversations, and the nice feeling that the whole trip had been worth it.
I hope you can probably tell how much fun I had. But beyond fun, it was also an important opportunity to shake hands with leading experts in the field and meet people - experienced or beginners - from all around Europe.
A lot of people asked me if it was worth attending, and my answer is yes. The same goes for overcoming the embarrassment and talking to completely unfamiliar people, because that is exactly how you meet new friends, future collaborators, and people who make the whole thing feel real. Never underestimate the power of showing up in person.
One of my favorite moments was when our DJ Giuseppe, seeing that I was fangirling around the van and vibing to the music, kindly offered to let me climb up there. It was the best! I also won’t pretend that I did not enjoy collecting all the swag from sponsors’ stands 🤩.
Everyone - organizers, sponsors, speakers, and of course, attendees did a great job turning this event into an unforgettable experience! Round of applause from me once again 👏
Next year Spring I/O is set to be held in Valencia for the first time ever. Fingers crossed, you will see a new version of this diary from me around that time.
Cheers, 🤸🏻♀️
Thanks to Tornike Onoprishvili for sponsoring this section of the blog.