Name: High Performance Spring Boot 3 on AWS Lambda
Start: 2025-06-16T16:00:00.000Z
Location: TU Wien, Freihaus HS1

Joint Meetup with [Scala Vienna](https://www.meetup.com/scala-Vienna/)

Agenda:
18:00 doors open
18:20 organizational stuff
18:30 - 19:30 Vaadin 24 in the real world - building the Java Vienna Raffle! - Sebastian Kühnau
19:30 - 19:55 Pizza break
19:55 - 20:00 Raffle
20:00 - 21:00 Mill: Untapped Potential in the Java Build Tool Experience - Li Haoyi

**Vaadin 24 in the real world - building the Java Vienna Raffle**
Vaadin ist ein Open-Source-Framework für die Entwicklung moderner Full-Stack-Webanwendungen – vollständig in Java, ohne Technologiewechsel zu JavaScript oder HTML. Aber was, wenn man Web Components oder UI-Bibliotheken integrieren möchte? In diesem Talk zeige ich verschiedene Wege, wie sich Komponenten aus externen Bibliotheken in Vaadin einbinden lassen – von nativen HTML Komponenten bis hin zu Web Components. In praktischen Beispielen zeige ich, wie das konkret funktioniert und wie wir das bei der Raffle-App gemacht haben, die speziell für die JUG Wien von Dominik und mir entwickelt wurde. Der Code steht im Anschluss natürlich zum Ausprobieren bereit.

Vaadin is an open-source framework for building modern full-stack web applications entirely in Java – no technology switch to JavaScript or HTML required. But what if you want to integrate existing Web Components or UI libraries? In this talk, I’ll walk you through several ways to bring external components into Vaadin – from native HTML Components to React-based integrations. A live demo will show you how it works in practice, using a raffle app Dominik and me built specifically for the JUG Vienna meetup. You’ll get access to the code so you can try it yourself afterward.

**About the Speaker**
**[Sebastian Kühnau](https://github.com/SebastianKuehnau)** ist seit zwei Jahrzehnten Java-Junkie und schon während seines Studiums Vaadin verfallen. Seit 2016 arbeitet er in verschiedenen Tech-Rollen bei Vaadin und unterstützt Kunden, maßgeschneiderte Webanwendungen zu entwickeln. Nebenher ist er zudem auf verschiedenen Events in und mit der Community aktiv.

**Untapped Potential in the Java Build Tool Experience**
The Java language is known to be fast, safe, and easy, but Java build tools like Maven or Gradle sometimes don't quite live up to that standard. This talk will explore what "could be": where current Java build tools fall behind modern build tools in other communities, in performance, extensibility, and ease of getting started. We will end with a demonstration of an experimental build tool "Mill" that makes use of these ideas, proving out the idea that Java build tooling has the potential to be much faster, safer, and easier than it is today.

**About the Speaker**
**[Li Haoyi](https://github.com/lihaoyi)** graduated from MIT with a degree in Computer Science and Engineering, and since then has been a major contributor to the open source community. His projects have over 10,000 stars on Github, and are downloaded over 20,000,000 times a month. Haoyi professionally built distributed backend systems, programming languages, high-performance web applications, and much more.

Java Vienna

Dominik Dorn

Nikolay Kushin

László Király

Gerald

Maximilian

Benjamin Maurer

Christian Wutte

Peter Haussl

Péter Biró

Swapnil

Sarah Brunner

Richard Lorenz

Mehmed Maljoki

Andreas Rosegger

Tobias Hochwallner

Szymon Sawicki

Adrian-Constantin Prelipcean

Christoph Sturm

Martin Merker

"Vaadin 24 in the real world" + "Engineering a better Java build tool"

TU Wien, Freihaus HS1

see the Java Vienna Event, please only register here OR there
https://www.meetup.com/java-vienna/events/306898838/

Scala Vienna User Group

Ajay

Jochen K.

Florian Bauer

Domonkos Lezsák

Rafael Cordones

Li Haoyi @ Java-Vienna

save the date!

Agenda:
18:00 doors open
18:20 welcome
18:30 OpenRewrite in a Nutshell: Scaling Upgrades with Practical Insights - Simon Gartner
19:30 break + networking
19:55 raffle
20:00 how John started to like TDD (instead of hating it) - Nacho Cougil
21:15 networking

**OpenRewrite in a Nutshell: Scaling Upgrades with Practical Insights**
Schnelle Upgrades, einfache Rezepte:

* **Was ist OpenRewrite?** Kurz & knackig.
* **Rezepte anwenden:** Composite Recipes, dryRun vs. run
* **Tech-Upgrades:** Wenig Downtime, klare Nachvollziehbarkeit (z.B. EAP-8)
* **Lesende Rezepte:** Code-Analyse leicht gemacht
* **Rezepte schreiben:** LSTs, Visitors, Praxisbeispiel
* **Rezepte wiederverwenden:** EAP-8, Quarkus, Spring Microservices

Ideal für effiziente, transparente Software-Upgrades.

**About the Speaker:**
**Simon Gartner - Softwareentwickler @ [Gepardec IT Services GmbH](https://www.gepardec.com/).**
Simon ist Softwareentwickler mit viel Erfahrung mit Legacy-Code. Er beschäftigt sich in seinen Projekten intensiv mit der Anwendung von OpenRewrite in der Praxis. Sein Fokus liegt bei der automatisierten und reproduzierbaren Durchführung von Migrationen. Simon konnte mehrere Modernisierungsprojekte, wie Frameworkupgrades, effizient und innovativ meisten.

**how John started to like TDD (instead of hating it)**
Let me share a story about how John (a developer like any other) started to understand (and enjoy) writing Tests before the Production code.

We've all felt an inevitable "tedium" when writing tests, haven't we? If it's boring, if it's complicated or unnecessary? Isn't it? John thought so too, and, as much as he had heard about writing tests before production code, he had never managed to put it into practice, and even when he had tried, John had become even more frustrated at not understanding how to put it into practice outside of a few examples katas 🤷‍♂️

Listen to this story in which I will explain how John went from not understanding Test Driven Development (TDD) to being passionate about it... so much that now he doesn't want to work any other way 😅 ! He must have found some benefits in practising it, right? He says he has more advantages than working in any other way (e.g., you'll find defects earlier, you'll have a faster feedback loop or your code will be easier to refactor), but I'd better explain it to you in the session, right? Ah! And if you think everything will be theoretical, no! **Get ready to see code examples with Spring Boot**.

PS: Think of John as a random person, as if he was even the speaker of this talk 😉 !

**About the Speaker**
**[Nacho Cougil](https://github.com/icougil)** is a software engineer from Barcelona, fan of TDD and XP practices. He has been working with Java and other web technologies before the effect 2000 and had experience in different roles in the IT world now working at Dynatrace writing code to monitor applications. You may probably meet him before as founder of the Barcelona Java Users Group & the Java & JVM Barcelona Conference ( JBCNConf ). He enjoys spending time with his family, playing sports & improving his eXtreme Programming skills.
Nacho is the founder of the [Barcelona Java User Group](https://github.com/barcelonajug) and a Java Champion.

Marian Dan

Thomas Scheibelhofer

Damjan Gjurovski

Ande Hofer

Görge Albrecht

Mira Haselberger

MilanG

Bernd Schlapsi

Georg M

Andrei Nagy

schakmann rene

Gerhard Keplinger

Thomas Mertes

Matthias Schmid-Kietreiber

Philipp Weixlbaumer

Gyula Molnar

"OpenRewrite in a Nutshell" + "how John started to like TDD (w/ spring boot)"

Joint meetup with [AWS Vienna Meetup](https://www.meetup.com/amazon-web-services-aws-vienna/) !

Agenda

18:00 doors open
18:20 welcome
18:30 High performance Serverless Java on AWS - Vadym Kazulkin
19:30 Break
19:55 Raffle
20:00 How to develop, run and optimize Spring Boot 3 application on AWS Lambda - Vadym Kazulkin
21:15 Networking nearby

**High performance Serverless Java on AWS**
Java is for many years one of the most popular programming languages, but it used to have hard times in the Serverless community. Java is known for its high cold start times and high memory footprint, comparing to other programming languages like Node.js and Python. In this talk I'll look at the general best practices and techniques we can use to decrease memory consumption and cold start times for Java Serverless applications on AWS Lambda including GraalVM (Native Image) and AWS own offering SnapStart based on Firecracker microVM snapshot and restore and CRaC (Coordinated Restore at Checkpoint) runtime hooks. We'll also look into the SnapStart priming techniques which help us increase the Lambda performance and explore how AWS Lambda Profiler for Java can help us identify this potential. We'll also explore the impact of the SnapStart snapshot tiered low-latency cache on the cold start times.

I'll also provide Lambda functions performance (cold and warm start times) benchmarking for:

* Deployment package sizes
* Lambda memory settings
* Java compilation options
* Managing Lambda dependencies with Lambda layers
* Choice of garbage collection algorithm
* Choice of hardware architecture x86 vs arm64
* HTTP (a)synchronous clients

**How to develop, run and optimize Spring Boot 3 application on AWS Lambda**
In this talk I will present and compare several options of how to run Spring Boot 3 application on AWS Lambda using the following framework or tools:

* AWS Serverless Java Container
* AWS Lambda Web Adapter
* Spring Cloud Function
* Custom Docker Image.

I'll also discuss strategies how to optimize cold start of such Lambda function with AWS Custom Lambda Runtime based on GraalVM Native Image and AWS own offering SnapStart based on Firecracker microVM snapshot and restore and CRaC (Coordinated Restore at Checkpoint) runtime hooks. Moreover I'll present various (SnapStart) priming techniques to reduce the cold start even further and explain the benefits of the snapshot tiered cache. Is Spring Boot native support of CRaC also a potential optimization? I'll also discuss optimization strategies for the warm start/execution time of the Lambda function.

Lechner Christian

Asdren Kuçi

Martin Prebio

Franz Stefan

Muhammad Salman

Mati Kepa

mykola.gurov

Martin Schwarz

High Performance Spring Boot 3 on AWS Lambda

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