On September 5, 2019, LINE Taiwan hosted the TWJUG community at its Taipei office. Technical evangelist Evan Lin welcomed attendees and introduced speakers Yoshida Shinya from LINE Tokyo and senior engineer Yuto Kawamura. The session covered ZGC for future LINE HBase and a mysterious JVM pause that degraded Kafka broker performance.

Yoshida explained that HBase—a Java‑based NoSQL store—relies on garbage collection that can trigger stop‑the‑world pauses. He compared G1GC, ZGC, and Shenandoah, noting that on 128 GB nodes ZGC delivered faster read and write throughput, though still experimental in Java 11.

Kawamura recounted a live‑service incident where Kafka produce latency spiked and Zookeeper sessions timed out. He traced the problem to prolonged STW pauses during garbage collection, using custom loops to reproduce the issue and confirm that JVM safepoint synchronization was the culprit.

The gathering underscored LINE’s commitment to developer engagement, with plans for over 30 events in 2019 under its new Community Program. Attendees were encouraged to join the LINE Developer Official Community for updates, while the insights shared promise to inform future JVM tuning and Kafka reliability strategies.