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This pattern has many similarities with the Shared database pattern.



Set up a new database and use synchronization mechanisms to move data between the existing and new database. The pattern assumes that data in the new database will be migrated back to the existing database. A variation of this pattern only replicates from existing data to new: Replicated database. The synchronized database pattern can be used to synchronize all or just some data between databases.


  • reduced MRP
  • new features early
  • partial replacement possible
  • new database can be on a different platform and have a different structure than existing db.
  • less need for migration


  • can be brittle
  • corrupt data
  • testing


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  1. Sep 19, 2009

    A one way replication gives some very different results:

    • The migration scripts will be needed by the final release anyway, so this is not a waste of effort. As a matter of fact, the strategy will ensure that the migration scripts have been thoroughly tested and remove the potential for very nasty surprises on the day of the release
    • It gives no risk of corrupting data, but it can risk exposing confidential data to unauthorized users.
    • It only allows you to actually release read-only functionality

    Should this be a different pattern, or a modification of the Replicated database pattern?

  2. Sep 19, 2009

    This discussing is easier solved if we discuss the different key system features/characteristics we try to solve by adding a database, i.e.

    • persistence
    • queries
    • transactions
    • integration
    • (add your favorite one..)

    If we look at each of the characteristics, there are quite simple and capable strategies which solves the problem at hand (possibly except integration solved at the database layer). Good experience and solutions are easily found at web-scale companies like Amazon and Google..

    1. Sep 19, 2009

      A good source for how to leverage legacy data with these technologies would be handy.