When a minor version of a database engine is deprecated in Amazon RDS, we will provide a three (3) month period after the announcement before beginning automatic upgrades. At the end of the this period, all instances still running the deprecated minor version will be scheduled for automatic upgrade to the latest supported minor version during their scheduled maintenance windows.
When a major version of database engine is deprecated in Amazon RDS, we will provide a minimum six (6) month period after the announcement of a deprecation for you to initiate an upgrade to a supported major version. At the end of this period, an automatic upgrade to the next major version will be applied to any instances still running the deprecated version during their scheduled maintenance windows.
Once a major or minor database engine version is no longer supported in Amazon RDS, any DB instance restored from a DB snapshot created with the unsupported version will automatically and immediately be upgraded to a currently supported version.