Zend_Cloud_DocumentService abstracts the interfaces to all major document databases - both in the cloud and locally deployed - so developers can access their common functionality through one API. In other words, an application can make use of these databases and services with no concern over how the application will be deployed. The data source can be chosen through configuration changes alone at the time of deployment.

Document databases and services are increasingly common in application development. These data sources are somewhat different from traditional relational data sources, as they eschew complex relationships for performance, scalability, and flexibility. Examples of document-oriented services include Amazon SimpleDB and Azure Table Storage.

The Simple Cloud API offers some flexibility for vendor-specific features with an $options array in each method signature. Some adapters require certain options that also must be added to the $options array. It is a good practice to retrieve these options from a configuration file to maintain compatibility with all services and databases; unrecognized options will simply be discarded, making it possible to use different services based on environment.

If more vendor-specific requirements are required, the developer should extend the specific Zend_Cloud_DocumentService adapter to add support for these features. In this manner, vendor-specific features can be called out in the application by referring to the Simple Cloud API extensions in the subclass of the Simple Cloud adapter.