Talk held at DevOps Gathering 2019 in Bochum on 2019-03-13. Abstract: This talk will address one of the most common challenges of organizations adopting Kubernetes on a medium to large scale: how to keep cloud costs under control without babysitting each and every deployment and cluster configuration? How to operate 80+ Kubernetes clusters in a cost-efficient way for 200+ autonomous development teams? This talk provides insights on how Zalando approaches this problem with central cost optimizations (e.g. Spot), cost monitoring/alerting, active measures to reduce resource slack, and automated cluster housekeeping. We will focus on how to ingrain cost efficiency in tooling and developer workflows while balancing rigid cost control with developer convenience and without impacting availability or performance. We will show our use case running Kubernetes on AWS, but all shown tools are open source and can be applied to most other infrastructure environments.