Got legacy software on Virtual Machines or Bare Metal on-prem or in cloud, maybe even Windows OS? Many of the developers who wrote it left the company? Probably code changes are avoided, security or MTLS are out of the question, and forget about circuit breaking. Despite Service Mesh and Kubernetes are obvious couple, it's actually a great fit for your legacy VMs, you can have modern software development patterns and operations practices without changing your code today (or next week).