Linkerd, an open source service mesh built on Scala, Finagle, and Netty, has seen steady adoption since its inception in 2016, and is now used in production by companies like Salesforce, CreditKarma, and FOX. In this talk, we describe lessons learned in adapting these technologies to the cloud native ecosystem. We discuss how some of Finagle's core components, like Vars and Activities, are used to provide robust and dynamic behavior in Linkerd. Finally, we explore some of the operational challenges of using the JVM in cloud native environments, which have radically different constraints than those which the underlying technologies were designed for.