Having worked for IB and done several migrations there, I can tell you that the answer is less of a technical one and more of a business one. Most people would answer this question from a hardware/software perspective (preparing the servers, setting up the databases, framework, etc.), but what IB is most interested in when doing a migration is preventing the loss of traffic or revenue. Second to this is making it easier to add features and maintain the site at minimal cost. This means moving servers in house (from the various hosting companies where the sites were hosted before IB bought them), converting them to standard platforms (95% of the time, LAMP - Wordpress for blogs, MovableType for content heavy sites, vBulletin for forums) A good way to approach this question is something like this: "When starting a migration, the first concern is to make sure that the site in question doesn't lose any traffic or revenue during the process. This means making sure that any incoming links are preserved or 301 redirected to new ones in the case that the site has a new URL structure. We also want to make sure that the site performs as well as or better on the new platform (hardware and/or software), so that we don't anger users or get penalized by search engines. We also want to make sure that the new platform makes it easy to add new functionality in the future without requiring large amounts of dev time. "