The Great Sidecar Debate

Sidecars, long the defining characteristic of the service mesh, are now the subject of its latest debate. While Kubernetes itself has recently added native support for sidecar containers, for service meshes, the question remains: does this architecture still hold water? Or, in the world of ambient and eBPF, are sidecars an antiquated approach already surpassed?

In his KubeCon talk, Buoyant CEO, William Morgan, takes a pragmatic and engineering-focused approach to the debate. Every engineering choice is ultimately a tradeoff, so what are the tradeoffs at play here? Are there situations where sidecars provide value vs alternatives? Situations in which they suffer by comparison? He evaluates the practical considerations for service meshes: resource consumption, operational considerations (e.g. blast radius), security considerations (e.g. threat models), and more, and attempt to paint a comprehensive and unbiased picture of the pros and cons between approaches.