Starting today,you can upgrade your RDS PostgreSQL database instance from major version 9.3 to 9.4 with just a few clicks on the AWS Management Console. PostgreSQL 9.4 offers several performance and feature benefits over PostgreSQL 9.3 for many customers. This includes support for the JSONB datatype, which allows you to manage schemas more flexibly. We encourage you to read about what's fresh in PostgreSQL 9.4 and test your application for compatibility before you upgrade your databases to version 9.4. To upgrade, or simply select the "Modify" option on the AWS Management Console corresponding to the DB instance you want to upgrade,choose the version of PostgreSQL 9.4 you want to upgrade to, and proceed with the wizard. Some of the earlier versions may not be available for upgrade to avoid the possibility of upgrading to a version that was released by the community before your current version. The upgrade may be applied immediately (whether you select the "Apply Immediately" option), and during your next maintenance window (by default). Please note that in either case,your database instance will believe an availability impact for a few minutes as the upgrade completes, and your database instance is rebooted. Please review the AWS User Guide to memorize more.
Source: amazon.com