Strimzi makes it easy to run Apache Kafka on Kubernetes. But persistent volumes and high-throughput cross-zone traffic can quietly become major cost drivers. In this talk, we’ll show how you can use OpenCost and NetObserve to build an open source, cost-aware view of our Kafka infrastructure — and how we tuned it to be leaner and smarter. While OpenCost doesn’t track network costs out of the box, we’ll show how to extend it with NetObserve data to estimate cross-zone network costs, attributing them directly to the pods generating the traffic. OpenCost can also help us to monitor compute and storage costs. We’ll share an open-source-driven playbook for cost-effective Apache Kafka on Kubernetes, informed by real-world experience and actionable strategies, without relying on proprietary tools or commercial observability platforms.