Scaling A/B Testing on Netflix.com with Node.js

Running Dozens of A/B Tests on a Node.js UI

Netflix is moving its website UI layer to Node.js, and the migration is forcing the UI engineering team to rethink how it builds and runs A/B tests. At the company's third JavaScript Talks event in Los Gatos, Calif., engineers Alex Liu and Micah Ransdell laid out the patterns they've developed to keep multivariate testing manageable when the site runs hundreds of experiments per year.

The core challenge is scale. Each A/B test adds state and branching logic to the UI, and doing that naively leads to code that's hard to change and slow to iterate on. The talk covered how Netflix structures its Node.js services to separate experiment logic from feature code, which lets product teams ship new UI variations quickly without turning the codebase into a tangle of conditionals.

Slides from the talk are available online. The team is also presenting its UI testing and Node.js work at NodeConf.eu (Sept 7–11, 2014), jQuery Chicago (Sept 12–13, 2014), and HTML5DevConf (Oct 20–21, 2014). Recordings of previous JavaScript Talks are on the Netflix UI Engineering YouTube channel.