From New Relic’s August 2014 blog post:
[W]e didn’t try to create a full PaaS framework all at once. Though this may be our eventual goal, it wouldn’t have solved the immediate deployment problem.
We did not begin Dockerizing our applications by starting with those that have the highest data volume. Rather, we started with our simplest internal Web apps, particularly stateless things that could scale horizontally. Our early testing showed that high throughput apps are not a good choice for your first Docker deployment, due to the Docker network stack. […]
We didn’t implement dynamic scaling or service discovery. We decided to assign ports statically to each application, using a port registry. This let us pre-configure load balancers for an application across a pool of servers and let health checks determine where it is being served. It also let us easily preconfigure our monitoring applications.
[…]
We used Docker to separate builds from deployments, a strategy that aligns well with Docker’s architecture: Build jobs ship things to a Docker registry, and deployments pull images from a registry and execute them onto servers.
How are things going now? One wonders.