In an article I read from the NY Times, Salesforce.com may be making a play to banish Oracle as a supported platform. However, the system which might be interesting would be a PostgreSQL, or in memory database, acts as a local cache for the transaction based system, clears the local database records/cache after it uploads the ‘staged’ data from the local database to a cloud database where the data is ultimately stored. The activities on the local database should be fast, and the cloud database is a) data that may be transformed to any cloud based solution vendor(s), if necessary, if an SOA is built on top of the local database which communicates with the cloud via APIs. b) enables a local data-mart, if not transferred in real time, i.e. use a nightly transformation and have access to “day of” BI on a limited set of local data, c) again transaction performance and data segregation of the warehouse. This architecture is already in use at many firms, but I wanted to call it out. Another option is to use two cloud database solutions, one ‘local’ to your region, and one globally dispersed for performance and redundancy using an ETL, although I am not convinced this would be a great architecture.  The second cloud tier can be a transformation from the first for regulatory archiving, if required by law either for finance or DR (Disaster Recovery) policy.