Systems

The longest day of the year is comming and let's another Kotlin meetup. This time we geather at N26! **⚠️⚠️⚠️ Due to a venue policy please submit the following form for additional details. Without it, you won't be allowed inside the venue:** https://forms.gle/XjqVXkD3FARCM6jA8 **Line-Up:** 👉 **TestBalloon: Kotlin testing is easier (and more fun) than you think** *by Oliver Okrongli* You want an easier way to write tests? Parameterize tests in plain Kotlin? Reuse a series of tests? Easily extend own your test setup? Have first-class support on all platforms? All without struggling with a huge framework API? TestBalloon is a new test framework that brings the power of Kotlin to your test setup. With a small-surface API, a hierarchical test structure and an extensible DSL, TestBalloon makes Kotlin testing easy, even at scale. Oliver, the author of TestBalloon, will show testing patterns and strategies and lots of practical examples, ranging from simple unit tests with less boilerplate to advanced testing with coroutines and generated data. This talk is based on insights first presented at KotlinConf 2026 in Munich. At the end of this talk, you’ll be able to firmly the answer the question: "How can I master Kotlin testing with ease, and make my team release with joy and confidence, every time?" 👉 **One Topic to Rule 'Em All** *by Yonatan Karp-Rudin* Kafka delivered every event exactly once, in order, and lost nothing. So what broke? This talk follows that question into the gap most event-driven systems leave open: what actually guarantees the order your domain depends on, and what quietly doesn't. We start from a real log line, find the crack in an architecture that looks clean and ships fast, and rule out the fix everyone reaches for first. The cure turns out to be one sentence of domain thinking plus one line of config, though the Schema Registry will fight you on the way there. A live demo runs the bug and the fix back to back: same load, same hero, one change. If you build with Kafka, you have probably shipped a version of this bug. You will leave able to spot it and fix it before it pages someone. 👉 **TBD** **Speaker Bios:** 🗣 Oliver Okrongli Oliver has been shaping and creating software from backend to frontends. He is the author of TestBalloon, a next-generation Kotlin test framework. Before, he has helped to maintain Kotest, and contributed to several libraries of the Kotlin ecosystem as well as the Kotlin compiler. Can be found on GitHub (OliverO2) and the kotlinlang Slack (Oliver O). When not developing, he is most probably in deep talks, dancing, snowboarding or F18 catamaran sailing whenever he gets a chance. 🗣 Yonatan Karp-Rudin Yonatan Karp-Rudin is a Staff Engineer at Billie, building event-driven systems in Kotlin and Spring Boot. Off the clock, he plays with AI agents and builds random tooling, trying to hand off as much of his own workflow to a machine as he can. The rest of the time he's brewing mead or deep in a video game. **🗣 TBD**

We are happy to invite you to our next iOS meetup. This time we cooperate with the amazing 42 Berlin to share the knowledge and experience in iOS development. 18:00 Doors open 18:30 Welcome on campus **18:45** **— Sebastian Hagedorn, director of Engineering at Clue, presents "The Sensitive App".** Is your app really working, or just not crashing? “The Sensitive App” reports subtle bugs regardless of origin, and validates your assumptions in production so you don’t have to resort to guessing or praying. Learn how to turn your app into the first line of defense for your entire system’s health! **19:45** **— Dmitry Kurkin, lead Mobile Engineer at SuperNext, presents "Lessons that iOS Native Project could learn from ReactNative in agentic development".** We'll inspect the components of the React Native engine that provide faster feedback and boost agentic iterations.

Hallo liebe Java User Group Mitglieder! Diesmal haben wir zwei Bonner Kollegen zu Gast: * Martin Stoller: **Backend-Performance in Hochlast-Systemen: Lösungsansätze aus dem Data Engineering** * Andreas Monschau: **Zehn goldene Regeln, um dein Softwareprojekt zuverlässig zu ruinieren** Wir freuen uns euch zu sehen (virtuell oder vor Ort). Dank an [codecentric](https://www.codecentric.de/standorte/nuernberg) für Location, Bier und Pizza! ================= Viele Hochlast-Systeme beginnen als kleine, unscheinbare Prototypen - gebaut mit bewährten Mitteln wie relationalen Datenbanken, objektorientierter Business-Logik und klassischen Request-Response-Architekturen. Doch was passiert, wenn diese Systeme plötzlich nicht mehr Tausende, sondern Millionen von Requests bedienen oder Terabytes an Daten verarbeiten müssen? In der Praxis zeigt sich häufig: Klassische Optimierungen wie Caching, horizontale Skalierung oder effizientere Algorithmen stoßen irgendwann an ihre Grenzen, weil sie innerhalb desselben Paradigmas bleiben. Dieser Vortrag zeigt, warum echte Skalierbarkeit oft ein Umdenken erfordert. Anhand eines durchgehenden Praxisbeispiels wird schrittweise demonstriert, wie sich ein System von einer latenzoptimierten Request-Response-Architektur hin zu einem durchsatzoptimierten, analytischen System entwickelt. Dabei werden zentrale Konzepte aus dem Data Engineering greifbar gemacht - darunter Precomputation, Batch Processing, deklarative Verarbeitung und Denormalisierung - und in den Kontext klassischer Backend-Entwicklung eingeordnet. Die Teilnehmenden lernen, typische Grenzen traditioneller Architekturen zu erkennen und erhalten ein alternatives Denkmodell, um High-Throughput-Systeme gezielt und nachhaltig zu skalieren. ================= Softwareprojekte sind chaotisch, anstrengend und voller Überraschungen. Und ganz ehrlich: So soll es auch bleiben. Ordnung würde ja nur den Spaß verderben. Trotzdem gibt es immer wieder Menschen, die glauben, man könnte Projekte wirklich zu Erfolg führen… unglaublich, oder? Damit dir so etwas nicht passiert, zeige ich dir in diesem Vortrag, wie du ein Softwareprojekt in 10 einfachen Schritten zuverlässig an die Wand fährst. Die „goldenen Anti-Pattern für maximalen Projektschaden“ entstammen jedoch nicht meiner Fantasie, nein, sie werden in der Realität täglich mit beeindruckender Konsequenz praktiziert. Und das Beste: Sie wirken nachhaltig. Manche dieser Muster entfalten ihre volle Zerstörungskraft erst Monate später. Nachdem du alle Regeln kennengelernt hast, kannst du selbst entscheiden: Möchtest du sie weiterhin anwenden, oder vielleicht doch etwas verändern? Solltest du allerdings inspiriert sein, eines dieser Anti-Pattern künftig noch konsequenter zu leben… dann sollten wir uns nach dem Talk dringend unterhalten. ================= Dein Vortrag bei der Java Usergroup Nürnberg! Hast du dich in letzter Zeit in deinem Projekt oder privat mit einem interessanten Thema beschäftigt? Vermutlich ist das nicht nur für dich selbst interessant! Hast du Lust, selber einmal einen Vortrag bei der Java-Usergroup Nürnberg zu halten? Wir sind nicht nur auf Java-Themen fokussiert, sondern beschäftigen uns gern mit und um alles über Software Entwicklung und IT. Wir wollen bei der JUG nicht nur bekannten Speaker\*innen eine Plattform geben und die neuesten State-of-the-Art Technologien vorstellen. Wir freuen uns auch besonders, wenn wir Themen aus unserem technologischen (Arbeits-)alltag Raum geben zu können. Melde dich gerne bei uns, wenn du dazu Lust hast, wir geben wenn gewünscht gerne auch Hilfestellung bei der Vorbereitung!

Join us for the first meetup 100% dedicated to agentic analytics in Berlin. **The goal:** share real-world feedback between data teams on implementing analytics agents. **The format:** a roundtable with 4 data teams who have tested or deployed analytics agents using different solutions - Cortex, Dust, Hex, nao, Omni, Looker, or in-house tools. **[RSVP on Luma.](https://luma.com/ly17mjtj)** 📣 **Speakers of the night:** * [Marina Ariamnova](https://www.linkedin.com/in/marina-ariamnova/?utm_source=luma), Analytics Manager at SumUp - LangChain vs Dust * [Andrey Pushvintsev](https://www.linkedin.com/in/pushvintsev/?utm_source=luma), Staff Analyst at Miro - Claude + custom BI MCP * [Marielle Dado](https://www.linkedin.com/in/marielledado/?utm_source=luma), Senior Analytics Engineer at CarOnSale - Dataleap, Langdock, Claude + Snowflake Cortex MCP vs Secoda AI * [Andre Wagner](https://www.linkedin.com/in/andre-wagner/?utm_source=luma), Director of Data Analytics at Taxfix - Claude + custom plugin vs Looker The panel will be moderated by [Christophe Blefari](https://www.linkedin.com/in/christopheblefari/?utm_source=luma), founder of [nao Labs](https://getnao.io/?utm_source=luma). **Agenda** 6:30 PM: Doors open 7:00-8:00 PM: Roundtable 8:00-10:00 PM: Drinks and Networking **About our sponsor:** [nao Labs](https://getnao.io/?utm_source=luma) helps teams build and operate AI coworkers for analytics and operations. Their platform focuses on practical, production-ready agent workflows so companies can turn LLM capabilities into measurable business outcomes. **About our host:** [Trawa](https://trawa.energy/?utm_source=luma) is a Berlin-based energy platform helping businesses access cleaner and more cost-efficient electricity. By combining software, data, and energy market expertise, trawa enables companies to optimize procurement and better manage energy costs. Want updates or more info? Subscribe to our newsletter: [databerlin.substack.com](https://databerlin.substack.com) Follow us on LinkedIn: [Data Berlin on LinkedIn](https://www.linkedin.com/company/data-berlin/?utm_source=luma) Looking for a job? [databerlin.net/jobs](https://databerlin.net/jobs) Join our Slack community: [Data Berlin Slack](https://join.slack.com/t/databerlin/shared_invite/zt-2q6j9x0z8-~sG7o3Q8S2j4j5gXg2yHlw)

Zapraszamy wszystkich na bezpłatne zajęcia medytacji w Berlinie dla Polaków. Po całym dniu pracy,zajęć w szkole, czy też dodatkowych aktywności. W stanie medytacji możemy zaznać chwili relaksu oraz wyciszenia. To wspaniała metoda, na pozbycie się wszelkich emocjonalno- mentalnych napięć powstałych w ciągu dnia,zniwelowanie stresu, czy też zmęczenia naszego organizmu. Co tygodniowe zajęcia medytacji, które odbywają się w kazdy czwartek o godzinie 19.00 w centrum Sahaja Yogi które znajduje się przy ulicy Behaimstraße 8 (Hinterhof )10585 w Berlinie.

The Language Café is primarily aimed at people who are struggling with their mental health which can make it hard to go to regular courses. We want to create a safe space for everyone to learn and practise without pressure. Everyone is welcome! Please try to be on time so we can all get started together :) We mainly practise on a beginner/lower intermediate level and adapt to everyone's prior level of German. The Language Café will focus on teaching you the most important words and phrases and basic grammar in German. The content of the course is adapted to real life. (everyday life in Germany, dealing with authorities, etc.) We will cover different topics every week and you can join us anytime, since the topics do not necessarily build on each other. The Sprachcafé is for free. \*If you cannot make it please cancel your participation so someone else from the waiting list can join, thank you!\* \| \| \| \|

Please reserve your spot by registering on the below link : https://www.eventbrite.com/e/join-biggest-community-investors-founders-berlin-online-tickets-1988380688164?aff=meetup QUESTIONS ? Pls Reach out to; Rose - +971528033410 ( WhatsApp Only)

Welcome to Sunday Tech Coffee. This is a **networking** event for those in the tech industry in Berlin. We are usually inside and to the right. Ask the barista/bartender if you can't find us.

The Creative Code Jam is a monthly gathering of artists, makers, designers, illustrators, coders, musicians, performers, learners and anyone interested in the use of computing skills for artistic expression. The event is free and open to all, regardless of age, origin, gender or experience. The jam is an opportunity to meet likeminded people and get creative together in a relaxed and safe environment. Beginners and first-timers should feel especially welcome! WHAT SHOULD I EXPECT? **Bring a laptop** and/or anything you’d like to work on, whether it’s a personal project, an experiment, or a skill you want to learn. You can come with friends or meet new people here. There’s no set agenda: some people code, some sketch ideas, some collaborate, and others just chat and get inspired. SCHEDULE Doors open at noon, then we’ll have quick introductions so everyone can share what they’re planning to work on. Note: arriving on time is the best way to hear what others are up to ;) Around 6 pm, we gather to share what we’ve worked on during the day. BEGINNERS WELCOME! If you’re new to creative coding, we'll be happy to help you get started, and you can find beginner-friendly resources at [creativecode.berlin/learn](http://creativecode.berlin/learn). THIS IS YOUR SPACE We do our best to create a welcoming environment for all people regardless of race, ethnicity, color, religion, gender identity, sexual orientation, national origin, age, disability, or genetics. People from group generally underrepresented in open-source, art, and technology fields are warmly encouraged to come by. And if you know someone who might enjoy this meetup but isn’t sure it’s for them, let them know they’ll be welcome! SAFE SPACE POLICY We support the Berlin Code of Conduct: https://berlincodeofconduct.org/ Please make sure you agree with its content. ABOUT MotionLab.Berlin MotionLab.Berlin is Germany’s premier Innovation Hub & Makerspace – an ecosystem for Hardtech, art, creativity, and entrepreneurship. They are an international community with access to state-of-the-art machinery, prototyping machines, coworking spaces, offices, and production facilities. More info: https://motionlab.berlin/ ACCESSIBILITY MotionLab is located on the ground floor, with bathrooms on that same level, although unfortunately they are too small for wheelchairs. FOOD MotionLab has drinks and snacks for sale. Bio food can be found on LPG at Bouchéstr (\~200m). Their cantine has vegan, vegetarian and other food options until 8pm. DO I NEED TO SPEAK GERMAN? We speak mostly English so international guests are more than welcome! Our team also speaks French, Turkish, Italian, Spanish, Dutch, Finnish and German... though language availability may vary depending on which organizers are present :) CONTACT Raphaël de Courville team@creativecode.berlin +49 176 700 70572 or get in touch via [creativecode.berlin](https://creativecode.berlin/)

\* PLEASE NOTE: THIS TOUR WILL TAKE PLACE ON TWO OCCASIONS, EACH VERSION ENTIRELY DIFFERENT - BUT WITHIN A SIMILAR FRAME OF THINKING Saturday, June 20th and Saturday, June 27th, both 13:00 - 15:00 PLEASE SCROLL BELOW TO SEE DESCRIPTION OF SECOND TOUR "The Politics of Memory" is a three-stop tour exploring how acts of collecting, archiving, and exhibiting shape what is preserved and who has the power to decide. Beginning with the historical Wunderkammer, or cabinet of curiosities, the tour examines the origins of collection and display, questioning the hierarchy between collector and collected and challenging traditional systems of classification. It then turns to contemporary approaches to documentation and preservation, exploring how galleries continue to select, organize, and legitimize what is considered worth remembering while raising questions about responsibility once exhibitions end. Finally, the tour considers the archive as a contested and subjective space, reflecting on preservation as an act that can both protect and transform its subjects, and revealing how decisions about what is saved, displayed, or forgotten are ultimately decisions about which stories, truths, and histories are allowed to endure. \*Itinerary is subject to change On our standard tours, we guide you through several thought-provoking presentations in the form of both group and solo exhibitions; on special tours, we have the fortune of visiting an artist studio and gaining insight into the artistic process. Whether galleries, museums, or artist studios - the goal is always to open your mind, discover new ways of thinking, and make new friends! Meeting location: In front of König Galerie at Alexandrinenstraße 118–121, 10969, Berlin Time: 13:00 - 15:00 Please do not go inside the gallery prior to the starting time - it is important that we all begin the journey together. Saturday, June 27th 13:00 - 15:00 \*Acts of Memory\* explores the relationship between personal and collective memory, asking how lived experience shapes identity and what happens when individual histories come into tension with broader cultural narratives. Moving from archives of everyday images and cultural objects to works that revisit inherited political histories, the tour examines memory as something that is not only preserved but constantly reinterpreted. It considers how familiar visual languages can evoke longing, discomfort, or contradiction, and how artists use them to navigate complex relationships with the past. The tour concludes by focusing on the body as a site of memory, exploring how desire, identity, and gender are shaped through cultural narratives, symbolism, and lived experience. Together, the works question who is remembered, what is forgotten, and how memory continues to shape our understanding of ourselves and our histories. Meeting location: In front of Between Bridges, Adalbertstraße 43, 10179, Berlin Please call +49 0157 34341803 if youare running late or can’t find the group.

**This event is taking place online.** You know AI is shifting how work happens. But where does it fit in *your* team? Maybe you're using it somewhere and not sure it's working. Maybe you've held back because you're not confident. Maybe you can't agree on when to use it. Welcome to an honest decision-making conversation. 17:00 — Intro 17:05 — When do you use AI, when not? (In your teams, right now) What's missing to decide well together? 17:15 — Simple frameworks for making these choices 17:30 — Examples and take-aways 17:45 — Questions and wrap-up This is the second session in our series. We'll test some decision-making frameworks together and learn what actually helps your team choose clearly, because the best decisions come in good company. Facilitator: Anca Trif Language: English Capacity: 10 attendees **Join Here**: https://meet.google.com/gmp-ywbd-qqm

At OpenSpace Networthing entrepreneurs from diverse disciplines, industries and nations meet to collaboratively develop solutions for challenges presented by participants. This month we will dive deeper into building digital products with Vibe Coding & AI with Varun Jain. We are building a networking-App: The "Tinder for Entrepreneurs" If you want to offer a workshop or present a topic for our members, write an email to alejandro.wagner@mlp.de Entrance is free! Bring in your expertise instead.

Join Us for a Morning Swim at Humboldthain Outdoor Pool! Hey everyone, We are doing another relaxed swim meet-up at Humboldthain outdoor swimming pool, and I'd love for you to join! We'll be gathering for a casual 30-minute swim - nothing competitive, just a chance to enjoy the water and start the day on a refreshing note. Afterwards, if you're up for it, we can go to a nearby cafe for a coffee and chat, but no pressure - totally optional! 📝 **Bring** - ID/passport (mandatory, checked by the pool staff) !!! - swimsuit - towel - 1 Euro coin (for a locker) - ticket is around €5.50 (buy online or at the pool) **RSVP** Please un-RSVP ❌ if you cannot come! Otherwise we would unnecessarily wait for people to never show up. 📍**Where** At the pool entrance (see the map pin) and wait for 15 min for people to gather. You need to enter Humboldthain park. 🎟 **Pool tickets** [https://www.berlinerbaeder.de/baeder/detail/sommerbad-humboldthain/](https://www.berlinerbaeder.de/baeder/detail/sommerbad-humboldthain/) ☕ **Coffee** A wonderful coffee shop a few minutes away from the pool [https://maps.app.goo.gl/os3WHTSfYzbDyKQh7?g_st=ac](https://maps.app.goo.gl/os3WHTSfYzbDyKQh7?g_st=ac) Looking forward to seeing you there!

Unser Verein berlinCreators e.V. trifft sich jeden Freitag ab 18 Uhr im Makerspace. Wir haben Gruppen rund um Elektronik, 3D-Druck, Nähen, Programmieren, Retro Computer. Egal ob Anfänger oder Profi – hier seid Ihr Willkommen. Ihr könnt mit anderen fachsimpeln, Euch inspirieren lassen oder auch mit unserer Hilfe Eure ersten Projekte starten. Wenn Ihr Euch bei uns wohlfühlt und Mitglieder bei den berlinCreators werden möchtest, freuen wir uns. Kommt vorbei, lernt den Space, uns und die Möglichkeiten kennen.

We are going to build together with all the CLIs! E will be doing it at Columbus Code and Coffee Agenda --- Hosted By James Power, Organizer Pete Gordon, Organizer Just a Software Guy in the age of the Internet. Complete your event RSVP here: https://gdg.community.dev/events/details/google-gdg-columbus-presents-ai-improv-lets-build-a-game-together-with-claude-code-codex-and-gemini-and-be-the-judge/.

We are bringing Microsoft Build sessions to Columbus Ohio! The Central Ohio Azure Meetup and Central Ohio .NET Developer's Group (CONDG) are coming together to bring some of the labs and breakouts from Microsoft Build to your backyard. In this free, 1 day event, you are going to Build stuff with us! And yes, there will be free food. Please RSVP via [Microsoft Build //localhost:columbus | Microsoft Reactor](https://developer.microsoft.com/en-us/reactor/events/27247/).

Join the CONNECTED Westerville Mastermind Group for a dynamic afternoon of B2B networking! This event is perfect for professionals looking to expand their business connections, share insights, and foster collaboration within the community. Whether you are a seasoned entrepreneur or just starting out, this event offers a valuable opportunity to exchange ideas, build relationships, and grow your network in a supportive environment. Connect with like-minded individuals, explore potential partnerships, and discover new opportunities for professional growth. Don't miss out on this chance to enhance your business network and take your career to the next level with CONNECTED Westerville Mastermind Group! We meet the 4th Monday of every month from 11am-1pm. Welcome and general networking from 11am - 11:30am with core meeting 11;30 - 12:30 and a final round of networking from 12:30 - 1pm.

**Important time note:** Please plan on arriving between 5:30 and 6:00 as the elevators lock after 6 and you'll need to message us and we'll need to come get you. The building address is 4450 Bridge Park The entrance is 6620 Mooney St, Suite 400 You will need to scan your ID at the door to get a visitor badge. **Abstract** *Customize the IDE: Building Extensions for Visual Studio Code* Visual Studio Code is one of the most widely used development environments today, and much of its flexibility comes from its extension ecosystem. Extensions allow developers to customize the editor with new features, integrations, and workflow improvements tailored to their needs. In this session, we’ll cover what extensions are and the different types available, including full extensions written in TypeScript or JavaScript, along with lighter-weight extensions such as color themes, language packs, language support, code snippets, and keymaps. We’ll also look at practical reasons a developer might create an extension, from automating repetitive tasks to adding custom tooling. The session includes a hands-on walkthrough of creating a new extension, testing it locally, and understanding the basic project structure. We’ll close with a brief overview of how extensions are packaged and published to the Visual Studio Marketplace and other distribution options. **YouTube Link** TBD

WQC has weekly Thursday night social nights at the Westerville Java Central. Come and grab a coffee and connect with the community: low stakes, chill environment, and tasty drinks. No registration is required; come as you are.

**Improving Office in Franklinton** Physical location: Improving Office 330 Rush Alley Suite #150 Columbus, OH 43215 Schedule: 6:00 p.m.: Socialize, eat, and drink. Improving will be providing pizza and beverages. 6:30 to 8:00 pm. Main meeting and presentation(s). Topic: This month Chris Pazsint will be talking about Agentic Coding. How does one use CLI Based Agents, and Agentic IDEs such as Cursor, Kiro, Antigravity? How to include agentic coding plugins for IDEs you already love such as Visual Studio Code. We meet on the last Monday of each Month. Presentations are given by members and friends of this group. If you would like to do a presentation (small or large) on a python topic, please contact Central OH Python at centralohpython@gmail.com

## 🤝 Host Information A co-hosted event by ProductTank Columbus & Women in Product Columbus 💡 About the Workshop AI adoption is stalling across organizations — not because of a lack of motivation or tools, but because it's fundamentally a behavior design challenge. This hands-on workshop applies proven Behavior Design models and methods to help you move from a vague organizational wish to boost AI adoption to 3-5 concrete, testable interventions you can act on starting tomorrow. Whether you're a product manager, on a product team, or just someone trying to get AI to actually stick at work, you'll leave with a clear picture of what's worth focusing on, what to ignore, and how to drive real, sustained adoption — no guesswork required. 🛠️ What to Bring Laptop: Fully charged and ready to go. AI Assistant: Have your favorite AI assistant pulled up. (Dom will be using Claude, but feel free to use whichever assistant you prefer!) 🍕 Logistics & Perks Food & Drink: Pizza and drinks provided! Parking: Plenty of free spaces available on-site. ###