We definitely took some inspiration from projects like synapse.

However, Finagle, the core tech behind linkerd, provides some extremely powerful tools to do things like:

- per-request routing to support things like "when I browse the site, use the staging version of the users service and production versions of all other services". (https://twitter.github.io/finagle/guide/Names.html#interpret...)

- request cancellation, so that when a user request timeouts downstream work can be reclaimed

- budget-based timeout management (https://twitter.github.io/finagle/guide/Servers.html#request...)

- circuit breaking (https://twitter.github.io/finagle/guide/Clients.html#failure...)

- etc, etc.

We think that offering these sorts of features in a sidecar model will be extremely powerful.

Netflix have something similar https://github.com/Netflix/Prana and I've got a Sidecar in Micro too https://github.com/micro/micro/tree/master/car. It's a solid model for integrating applications which you don't necessarily have client libraries for or don't speak the same protocol.