now-ab. Intriguing example of a Zeit Now microservice: now-ab is a Node.js HTTP proxy which proxies through to one of two or more other Now-deployed applications based on a cookie. If you don’t have the cookie, it picks a backend at random and sets the cookie. Admittedly this is the easiest part of implementing A/B testing (the hard part is the analytics: tracking exposures and conversions) but as an example of a microservice architectural pattern this is fascinating.