The conventional software running on network devices, such as switches and routers, is typically vendor-supplied, proprietary and closed-source; as a result, it tends to contain extraneous features that a single operator will not most likely fully utilize. Furthermore, cloud-scale data center networks often times have software and operational requirements that may not be well addressed by the switch vendors. In this paper, we present our ongoing experiences on overcoming the complexity and scaling issues that we face when designing, developing, deploying and operating an in-house software built to manage and support a set of features required for data center switches of a large scale Internet content provider. We present FBOSS, our own data center switch software, that is designed with the basis on our switch-as-a-server and deploy-early-and-iterate principles. We treat software running on data center switches as any other software services that run on a commodity server. We also build and deploy only a minimal number of features and iterate on it. These principles allow us to rapidly iterate, test, deploy and manage FBOSS at scale. Over the last five years, our experiences show that FBOSS’s design principles allow us to quickly build a stable and scalable network. As evidence, we have successfully grown the number of FBOSS instances running in our data center by over 30x over a two year period.