How Groupon migrated from a monolithic Rails app to a new Node.js infrastructure

The title was "I-Tier: Dismantling the Monoliths"

And it's actually not just about going from RoR to Node. The European operations are of nearly equal size and value as those in the US, and they were on a Java/Apache/PostgreSQL stack. I-Tier has been nearly as much about about unifying everything under one uniform architecture as it has about performance.