JCON EUROPE 2023

When writing new Java webapps, teams often have some nagging scaling doubts:

* How many users can my application simultaneously handle?
* How fast will my controllers dash out those JSON responses?
* How much memory, CPU or I/O does my application need?
* What is the most cheapest, but most fitting instance type for my app?

Surprisingly, there's very little advice out there on how to sensibly approach these questions in a practical way - apart from that deceiving gut-feeling which tells you that everything will be fine, by simply auto-scaling random Kubernetes pods into oblivion.

In this #almostnoslides session we're going to use an IDE, a pen tablet and a bit of OS tools & custom code to get a deep, practical understanding of the following scaling topics:

* Throughput: How to reliably find out to how many users your application will scale to
* Memory & CPU: How much (or how little) memory & CPU your Spring app actually needs
* Latency: How your Spring webapp would compare to a Counterstrike game server
* And much more

By the end of this talk, you'll have learned all the tools and, more importantly, solid load-testing processes that make you never worry about scale again. You will understand how to collect performance data, correctly interpret that data and thus understand exactly what happens in your Spring application in various load testing scenarios.