Gilt uses Puppet for configuration management across its infrastructure. It has around 1000 Puppet modules and uses tools like Puppetmaster, Puppet Dashboard, and an in-house External Node Classifier called Mothership. Changes are rolled out incrementally using a development, canary, and production process. Mothership also handles provisioning, assets management, and mapping hosts to Puppet modules. Lessons learned include keeping modules small and simple, planning for change like OS upgrades, and using multiple views in Mothership for logical vs physical infrastructure. Future plans aim to accelerate incremental deployments daily with easy rollbacks while maintaining 100% uptime.