Denis Magda: How Java Apps Litter Beyond the Heap and What We Can Do About That

Wednesday March 8, 2023

5:30-6:00: Food, Soda, Beer and Networking

6:00-6:15: Announcements

6:15-7:45: How Java Apps Litter Beyond the Heap (And What We Can Do About That)

As Java developers, we’re no strangers to the concept of garbage collection. Java apps generate lots of garbage which is meticulously cleaned by CMS, G1, Azul C4, and other types of collectors. However, the story doesn’t end with the Java heap. It only starts there. In fact, your application code constantly generates garbage and triggers collection cycles at the database and even hardware level.

In this session, we take the example of a typical Java application that uses PostgreSQL or YugabyteDB as a relational database and SSDs as a storage medium. From there, we will analyze how our apps litter beyond the boundaries of the Java runtime and what actions we can take to avoid surprises in production.

About Denis Magda

Denis started at Sun Microsystems and Oracle, where he built JVM/JDK and led one of the Java development groups. After learning Java from the inside, Denis joined the world of distributed systems and databases, where remained ever since. His experience spans from the development of distributed database engines and high-performance applications to training and education on the topic of “Java in the world of databases”.

7:45: Door prizes

8:00 Post-meetup networking

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Matt Raible: OAuth for Java Developers

Wednesday, 02/08/2023

5:30-6:00: Food, Soda, Beer and Networking

6:00-6:15: Announcements

6:15-7:45: OAuth for Java Developers

You can use OAuth to secure apps, APIs, and devices. OAuth has become increasingly popular, especially as developers are asked to knit together hundreds of apps and thousands of users in enterprise environments.

The Java ecosystem is vast, with over 10 million developers worldwide and an abundance of IDEs, build tools, libraries, and frameworks to make them more productive. In this quick session, I’ll provide you with a state of the OAuth ecosystem in Java. You’ll learn which frameworks support OAuth and which ones don’t. I’ll also offer some practical examples you can run in just a few minutes.

About Matt Raible

Matt Raible is a well-known figure in the Java community and has been building web applications for most of his adult life. For over 20 years, he has helped developers learn and adopt open source frameworks and use them effectively. He’s a web developer, Java Champion, and Developer Advocate at Okta. Matt is a frequent contributor to open source and a big fan of Java, IntelliJ, TypeScript, Angular, and Spring Boot.

He’s a member of the global JHipster development team and loves classic VWs. You can find him online at @mraible and

7:45: Door prizes from JFrog and Intellij

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Java meets TypeScript: building a full-stack reactive web app with Spring Boot


Wednesday, January 11 2023

Hello Denver Java Enthusiasts!

We’re starting at a new location in 2023 – Thrive Workplace in Cherry Creek. If you’re looking for a co-working location, they’re excellent!

We figure it’s best to start small and grow to a bigger space as needed. There is paid parking nearby the venue. We look forward to seeing you!

5:30-6:00: Food, Soda, Beer, and Networking

6:00-6:15: Announcements

6:15-7:45: Java meets TypeScript: building a full-stack reactive web app with Spring Boot

As Java developers, we know the benefits of type-safety when building apps. The problem? Usually, that type-safety ends when we leave the server. What if it didn’t have to be that way?

In this presentation, you’ll learn how to build a full-stack reactive web app through live code examples. We’ll use Spring Boot and Java on the backend and React with TypeScript on the frontend, connecting the two with the new Hilla framework from Vaadin.

About Marcus Hellberg:

Marcus is a long-time Java and web developer, always curious to learn new things. He’s interested in combining modern web technologies and Java. Marcus loves teaching developers about cool new technologies and has presented at over 100 conferences and user groups around the world. He currently leads Developer Relations at Vaadin.

You can find Marcus on Twitter at @marcushellberg.

7:45: Door prizes sponsored by JFrog and Intellij.

The post-event festivities are sponsored by Okta.

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Denver JUG Holiday Party at Rock Bottom Brewery

Wednesday, December 14th, 2022


Hello everyone and happy holidays!

We’d like to gather in-person in December and get back to fostering this lovely community. We’ll have lightning talks, an ugly sweater contest, and tasty beverages + snacks. If you’d like to do a 10-minute lightning talk (on any subject), please contact Matt Raible (

This is an in-person event at Rock Botton Brewery in downtown Denver.

Okta and Alchemy Technology Group are sponsoring this event.


  • 5:30-6:00: Food, Soda, Beer and Networking
  • 6:00-6:15: Announcements
  • 6:15-8:00: Lightning Talks
  • 8:15: Door prizes
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Venkat Subramaniam: Live In Person!!!

Wednesday, November 9th


This event will be held in Boulder at Rule 4(Directions):

3002 Bluff St #100
Boulder, CO 80301

It’s our first in-person event in quite some time and the speaker is Venkat! There will be no live stream or recording. It’ll be worth the drive and carpooling is a great way to build community. 😊

See the Boulder meetup page for more information. The information below is copied from this page.

Exception Handling in Functional and Reactive Programming

Functional and reactive programming is gaining popularity and use. One hurdle developers face using these approaches is in exception handling. Dealing with exceptions in these styles is confusing in the beginning and is often messy and error prone.

In this presentation we will step back and take a closer look at exception handling, about their role in functional and reactive programming, and discuss the dos and don’ts for exception handling. We will learn using concrete examples and live coding to illustrate the problem and the possible solutions.

Venkat is an international rock star, always insightful, informative, entertaining and a dry sly sense of humor!

About Venkat Subramaniam

Dr. Venkat Subramaniam is an award-winning author, founder of Agile Developer, Inc., and an instructional professor at the University of Houston.

He has trained and mentored thousands of software developers in the US, Canada, Europe, and Asia, and is a regularly-invited speaker at several international conferences. Venkat helps his clients effectively apply and succeed with sustainable agile practices on their software projects.

Venkat is a (co)author of multiple technical books, including the 2007 Jolt Productivity award winning book Practices of an Agile Developer. You can find a list of his books at You can reach him by email at or on Twitter at @venkat_s.

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Chris Love: Foundational Kubernetes and Container Security

Wednesday October 12th, 2022

Watch on YouTube:

5:30-5:45: Announcements

5:45-7:15: Foundational Kubernetes and Container Security

Security is a complex topic that can slow your team down, by adding too much complexity. This talk will cover some basic steps to improve your container and Kubernetes security posture. Come learn the foundational security basics that are critical for running applications in Kubernetes.

About Chris Love

Chris Love is a Google Cloud Certified hybrid Multi-cloud Fellow, and a Co-founder of Lionkube. He has over 25 years of software and IT engineering experience with companies including Google, Oracle, VMWare, Cisco, Johnson & Johnson, and others. As a thought leader within Kubernetes and the DevOps community, Chris Love has contributed to many open source projects including Kubernetes, kops (former AWS SIG lead), Bazel (contributed to Kubernetes rules), and Terraform (an early contributor to the VMware plugin). His professional interests include, IT culture transformation, containerization technologies, automated testing frameworks and practices, Kubernetes, Golang AKA Go and other programming languages. Love also enjoys speaking around the world about DevOps, Kubernetes, and Technology; as well as mentoring people in the IT and Software industry.

Outside of work Love enjoys skiing, volleyball, yoga, and other outdoor activities that come with living in Colorado. He’s also a practicing martial artist for over 20 years.

If you’re interested in having virtual coffee or have questions for Chris, you can contact him at @chrislovecnm on Twitter or LinkedIn.

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Melissa McKay: What Does a Java Developer Need to Know About DevOps???

Watch live on Youtube at


5:30-5:45: Announcements

5:45-7:15: What does a Java Developer Need to Know about DevOps???

A day in the life of a Java dev includes coding up new features and fixing bugs. But what happens after you’ve committed your code, and why would/should a developer care?

The process of developing and delivering an application to production can be an overwhelming task with a number of steps. Melissa will explain the DevOps methodology, discuss DevOps implementations, and walk through what all is involved. After learning about dependency management, CI/CD, supply chain security, production packaging and updates, it will be clear why a Java developer would (and SHOULD!) want to be aware of what is going on in their software delivery pipeline. Learn how a strong knowledge of DevOps will inform and guide your decisions as a developer!

About Melissa McKay

Melissa is passionate about Java, DevOps and Continuous Delivery. She loves sharing her knowledge with the community as a developer, speaker, and author. Melissa has been recognized as a Java Champion and Docker Captain, is an international speaker at events including Kubecon and DockerCon, and is co-author of the recently released O’Reilly title, DevOps Tools for Java Developers.

You can find Melissa on Twitter at @melissajmckay.

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Vaughn Vernon: Reactive Domain-Driven Design Made Explicit

Wednesday, August 10, 2022

Watch on YouTube:


5:30-5:45: Announcements

5:45-7:15: Reactive Domain-Driven Design Made Explicit

There is a better way forward than most developers have been taught by reading blog-driven example code. Those examples are often watered-down, how-to pitches on using some technical mechanism, but in their brevity provide some of the worst software design examples going. Even so, those examples are copied and embedded in the code that soon becomes a Big Ball of Mud. Since my “red book” was published, with the title Implementing Domain-Driven Design,” DDD has gained global popularity. That’s great and all, and certainly one of my authoring goals. Yet, with motivations in expediency, the vast majority of those who claim to use DDD have latched on to some of its tactical tools and called it good. And truly, it is not good. Certainly DDD is a “better way forward,” but only if applied with strategic thinking and engagement with business experts that leads to software innovation. It’s generally the technical patterns, such as CQRS and Event Sourcing, that attract developers. While very useful, such patterns are orthogonal to DDD, not the embodiment of it. In this 90-minute talk, full of live diagramming and expert advice, learn the essence of DDD and how to leverage the open source, purpose-build platform SDK that channels developers along the correct domain-driven path. This is uniformly achieved by enabling fluency of expression in rapidly-built Bounded Contexts and their supporting domain models that reflect accurate Ubiquitous Languages, all packaged into an instantly deployable Reactive, Event-Driven, fully-integrated, Microservices architecture. As a bonus, you’ll gain a vital understanding of how to maintain broadly distributed Domain Events and other elements for type- and version-safe information exchange. Success, win, success, win.

About Vaughn Vernon

Vaughn Vernon is the founder and chief architect of VLINGO XOOM, the OSS rapid development platform SDK supporting DOMA- and DDD-friendly Reactive, Event-Driven, and Microservices Architectures. A software developer and architect with more than 35 years of experience in a broad range of business domains, Vaughn is a leading expert in Domain-Driven Design (DDD) and champion of simplicity and reactive systems. Vaughn is the author of four books, including Implementing Domain-Driven DesignDomain-Driven Design Distilled, and Reactive Messaging Patterns with the Actor Model, all published by Pearson-Addison-Wesley. Most recently Pearson/Addison-Wesley has commissioned him for the Vaughn Vernon Signature Series, within which his fourth book Strategic Monoliths and Microservices— Driving Innovation Using Purposeful Architecture is published.

You can find Vaughn on Twitter at @VaughnVernon.

7:15-7:30: Q & A

The live streaming of this meetup is sponsored by Okta.

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Kito Mann: GraphQL Distilled


Wednesday, June 8th

Watch on YouTube:

5:30-5:45: Announcements

5:45-7:15: GraphQL Distilled

REST is all about endpoints that perform specific queries or operations. This works fine, but the client is limited by which queries have been exposed. What if the backend exposed the data, but the client could decide which subset of data it needed, and how to interact with that data? That’s the promise of GraphQL — simplify the back-end, give the client more power, and make it easier to evolve APIs.

When we take this approach, we also have more flexibility on the backend; we can use one or many different microservices together to provide a unified API. In this talk, we’ll explain what GraphQL is, how it works, and look at how easy it is to build GraphQL APIs using MicroProfile GraphQL.

About Kito Mann

Kito D. Mann is the Principal Consultant at Virtua, Inc. (, specializing in enterprise application architecture, training, development, and mentoring with microservices, cloud, Web Components, Angular, and Jakarta/Java EE technologies. He is also the co-host of The Stackd Podcast (, and the author of JavaServer Faces in Action (Manning). Mann has participated in several Java Community Process expert groups (including CDI, JSF, and Portlets) and is an internationally recognized speaker. He is also a Java Champion and Google Developer Expert in Web Technologies. He holds a BA in Computer Science from Johns Hopkins University.

You can find Kito on Twitter at @kito99 (

7:15-7:30: Q & A

The live streaming of this meetup is sponsored by Okta (

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Four Key Actions to Level Up the Lifecycle of Your Cloud-Native Apps

Wednesday, May 11th, 2022

Watch on YouTube:

5:30-5:45: Announcements

5:45-7:15: Four Key Actions to Level Up the Lifecycle of Your Cloud-Native Apps

Deploying 1440 times a day, in other words, one deploy per minute is not a sign that you’re on the right path. The challenge is: how can we have relevant app deliveries and how to innovate without breaking everything on my app?

As distinguished professionals, we need to be a step ahead, and not only understand the cultures and technologies but also, use all this ecosystem to positively impact the organization in a strategic and long-term manner.

In this talk, you’ll learn how to evolve your cloud-native app using four levels of maturity. With that, your apps can be delivered in a more secure, reliable, and fast-paced innovation in the cloud.

About Karina Varela

Karina Varela works with technologies for cloud-native apps development for over ten years. She’s been focused on business automation technologies, and she currently works at Red Hat as part of the Application Services business unit. She brings solid knowledge built by working with the development, architecture, delivery, and troubleshooting of enterprise software and platforms around the world.

You can find Karina on Twitter at @soujava (

About Otavio Santana

Empowering developers worldwide to deliver better software faster, scalable in the Cloud. Otavio is a passionate software engineer focused on Cloud and Java technology. He has experience mainly in persistence polyglot and high-performance applications in finances, social media, and e-commerce.

Otavio is a member of both Expert Groups and an Expert Leader in several JSRs and JCP executive committees. He is working on several Apache and Eclipse Foundation projects such as Apache Tamaya, MicroProfile, Jakarta EE, where he is leading the first specification at Jakarta EE with Jakarta NoSQL. A JUG leader and global speaker at JavaOne and Devoxx conferences. Otavio has received recognition for his OSS contributions such as the JCP Outstanding Award, Member of the year and innovative JSR, Duke’s Choice Award, and Java Champion Award, to name a few.

You can find Otavio on Twitter at @otaviojava (

7:15-7:30: Q & A

The live streaming of this meetup is sponsored by Okta (

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