Most large-scale web companies have evolved their system architecture from a monolithic application and monolithic database to a set of loosely coupled micro-services. Using examples from Google, eBay, and KIXEYE, this talk outlines the pros and cons of these different stages of evolution, and makes practical suggestions about when and how other organizations should consider migrating to micro-services. It concludes with some more advanced implications of a micro-services architecture, including SLAs, cost-allocation, and vendor-customer relationships within the organization.