Migration of Java EE applications from one application server to another is an activity that can vary from extremely simple to extremely complex. We got an opportunity to work on migration of a complex eCommerce platform from Oracle WebLogic application server to embedded Tomcat application server. It was a very complex eCommerce platform which was generating ~2 billion dollars revenue per year and consisting of 14 web applications running concurrently to process the orders from different channels and geographies round the clock. It was a spring-based platform which was built on top of an eCommerce product. This whitepaper talks about the problems which customer was facing with Oracle WebLogic server and the challenges in migrating it to an embedded tomcat server. It also talks about how we solved the problems, overcame the challenges one by one and did a successful migration.