The Amazon Relational Database Service (RDS) now supports version 5.5 of MySQL. This new version of MySQL includes InnoDB 1.1, and offers a number of performance improvements including enhanced use of multiple cores, better I/O handling with multiple read and write threads, and enhanced monitoring. InnoDB 1.1 includes a number of improvements over the prior version including faster recovery, multiple buffer pool instances, and asynchronous I/O.
As you can see from the screen shot above, you can start to use version 5.5 of MySQL by selecting it from the menu in the AWS Management Console when you create your DB Instance. In order to upgrade an existing DB Instance from MySQL 5.1 to MySQL 5.5 you must export the database using mysqldump and then import it into a newly created MySQL 5.5 DB Instance. We hope to provide an upgrade function in the future.
We do not currently support MySQL 5.5's semi-synchronous replication, pluggable authentication, or proxy users. If these features would be of value to you, perhaps you could leave a note in the RDS Forum.
To create a new MySQL 5.5 DB Instance, just choose the DB Engine Version of 5.5.8 in the AWS Management Console. Because it is so easy to create a new DB Instance, you should have no problem testing your code for compatibility with this new version before using it in production scenarios.