JDK 17 Memory Bloat in Containers: A Post-Mortem

When engineering teams modernize Java applications, the shift from JDK 8 to newer Long-Term Support (LTS) versions, such as JDK 11, 17, and soon 21, might seem straightforward at first. Since Java maintains backward compatibility, it's easy to assume that the runtime behavior will remain largely unchanged. However, that's far from reality. In 2025, our team completed a major modernization initiative to migrate all of our Java microservices from JDK 8 to JDK 17. The development and QA phases went smoothly, with no major issues arising. But within hours of deploying to production, we faced a complete system breakdown.