High-performance Java
❗❗ EVENT IS HELD IN-PERSON ONLY, IN PRAGUE ❗❗
After the break in December, we are starting 2026 with some serious stuff. In the first talk of the evening Jaromir Hamala will showcase their pretty unorthodox and performance focused Java in database implementation.
In the second, esteemed Java champion Rustam Mehmandarov will talk about modern API challenges.
Talk 1:
🎤 "Building a high-performance database in Java is impossible!" - by Jaromir Hamala, QuestDB
Or is it not? We built QuestDB, an open-source high-performance database, primarily in Java. What do I mean by 'high-performance' anyway? A single machine running QuestDB can ingest millions of rows per second and query billions. There is no magic here, just a lot of hard work and clever engineering. We focused on efficient data structures, parallel execution pipelines, and mechanical sympathy. Our Java is somewhat unorthodox: We aim for zero steady-state allocation, and we are not hesitant to jump to native code when needed.
In this session, I'll take you to the sausage factory and show you some of the techniques we use, including:
- SIMD-based optimizations from Java and native code for maximum throughput. We even build our own Just In Time (JIT) compiler!
- Implementing parallel execution pipelines to use multi-core processors effectively. - Our approach to off-heap memory management to achieve near-zero GC pauses.
- Crafting specialized data structures and algorithms suitable for high-performance Java.
I'll also answer the most common question people ask when they learn about our unorthodox Java: Why the heck do you use Java at all?!
Talk 2:
🎤 "API = Some REST and HTTP, right? RIGHT?!" - by Rustam Mehmandarov, SpareBank 1 Utvikling
Let's be honest: many of our so-called "REST" APIs aren't REST. They're just JSON-RPC over HTTP, with versioning challenges, brittle integrations, clumsy error handling, and a maintenance burden we all know too well.
Let's do something about this! We’ll go straight to the patterns that matter in production, tackling the real-world challenges head-on: building evolvable versioning strategies, designing sane error responses, providing clear API contracts, and demystifying the practical use of hypermedia (HATEOAS).
You'll leave with practical, battle-tested approaches for building APIs that are maintainable and scalable. We'll also discuss when to use REST and when alternatives like GraphQL or gRPC are a better tool for the job. All demos use Jakarta EE and MicroProfile, but the patterns can be applied to any modern web stack of your choosing.
When & where?
📍 The meetup will happen on Jan 27th, 2026, at Pure Storage office in Prague (Rohanské nábř. 661, 186 00 Karlín)
🕠 Door open at 5:30 PM and we will start with talks at 6:00 PM.
What's our plan for the evening?
The first part will be dedicated to the presentations on Java topics presented by speakers from leading software companies.
🍔🍻 After the talks we're planning a networking session to let the folks meet & chat informally, as well as some delicious food & drinks to keep you fueled throughout the evening!
Special instructions on how to get to the venue:
From Karlinske namesti you will walk straight in the direction of the Vltava river to the the Amazon Court building, Rohanske nabrezi 661.
There will be people from PureStorage in the main lobby who will direct you to their office in 1st floor. On the day of the event, we will send an email with a contact for those who arrive late or get lost.
PLEASE NOTE: at the Pure Storage office, all meetup attendees will be required to sign a generic NDA used for all office visitors and wear a visitor badge during the event - to be able to attend the meetup.
CZJUG Prague meetups are supported by:
Ataccama - AI-Powered Data Management
JetBrains - Pro Developer Tools
OmniFish - GlassFish and Jakarta EE support
Sky - Video streaming
Oracle
This event is supported by:
PureStorage - The leading Enterprise Storage Platform