Migrating 500 Nodes from Rackspace to Google Cloud with Zero Downtime

METRONOM, a multinational B2B Supermarket, migrated round 80 clusters with over 500 nodes from Rackspace in the UK to Google Cloud in Belgium, saving money and surviving Brexit. This is the story of how we managed this with zero production downtime, the problems and solutions we encountered on the way. An example of using Cassandra DCs to migrate data across geographical boundaries.