The Netflix tech blog discusses changing their billing infrastructure to be entirely in the cloud (AWS in this case):
Cleaning up Code: We started chipping away existing code into smaller, efficient modules and first moved some critical dependencies to run from the Cloud. We moved our tax solution to the Cloud first.
Next, we retired serving member billing history from giant tables that were part of many different code paths. We built a new application to capture billing events, migrated only necessary data into our new Cassandra data store and started serving billing history, globally, from the Cloud.
We spent a good amount of time writing a data migration tool that would transform member billing attributes spread across many tables in Oracle into a much simpler Cassandra data structure.
We worked with our DVD engineering counterparts to further simplify our integration and got rid of obsolete code.
Purging Data: We took a hard look at every single table to ensure that we were migrating only what we needed and leaving everything else behind. Historical billing data is valuable to legal and customer service teams. Our goal was to migrate only necessary data into the Cloud. So, we worked with impacted teams to find out what parts of historical data they really needed. We identified alternative data stores that could serve old data for these teams. After that, we started purging data that was obsolete and was not needed for any function.
All in all, a very interesting read on how to migrate large databases. Even if you’re moving from one version of a product to another, some of these steps might prove very helpful in your environment.