Happy Bear Software

On centralized database as a service

Thunderbolt labs have a great post on why sharing the database is an SOA anti-pattern. I agree with them. I've seen Rails applications that share a databse with different subclasses of ActiveRecord::Base in each for the same table. Some fields were used by one codebase, some by the other. Migrations were spread out across the different codebases. This is an example of broken encapsulation (and masochism).

You could make this work by wrapping your subclasses of ActiveRecord::Base into a private gem and using that to access the shared database instead of accessing it directly. The gem respository could be the place to store your database migrations for that table.

Using a library instead of accessing the database directly gives you the performance benefit of using the database and keeps the API encapsulated. If you were to change the library to use a JSON based HTTP API or a third party web service instead of the database, client code wouldn't know the difference.