Drupal 7 has entities and also has Entity Field Query. http://api.drupal.org/api/drupal/includes!entity.inc/class/EntityFieldQu...
Using EFQ has two important advantages :
- Multi Database support out of the box (Including MongoDB which is great for performance boosting)
- Special Caching using entity cache module
- Unified api which makes querying entities easier and more readable
- Extensibility , queries can easily be altered

Note : node is entity
There is also efq_views module
Simple usage guide :
http://treehouseagency.com/blog/tim-cosgrove/2012/02/16/entityfieldquery...