This endpoint is equivalent in purpose to the analogous EC2 endpoint we just looked at. Its input, however, is slightly different: it accepts a single instance ID as input and, as of the time of this writing, doesn't support filters.

This means that if our stack has multiple RDS instances—say, in a primary/replica setup—we need to make multiple API calls to gather information about each one of them. Not a big deal, of course, but a limitation to be aware of.

Once given a specific database instance ID, this service responds with the following code:

{"DBInstances"
   [{"DBInstanceIdentifier" "RDS123", "DBInstanceStatus" "available"}]}

The fact that a single instance comes inside a vector hints at the fact that filtering will be supported in the future. It just hasn't happened yet.