You want the
AWS Java SDK wrapped in a Servoy plugin.
An alternative option would be to create a small NodeJS application with the
AWS Javascript SDK and proxy your requests through it. Some advantages: you're coding in Javascript like you're used to, you can add features without rebuilding a plugin, you can keep up-to-date with SDK releases, as a dedicated service it scales and can serve more than one app, etc.
One of the current trends that is hot right now and which I really like is micro-services. It's trivial to spin up a server/app (in any language) that does one thing really well. Communicating via REST/JSON between services is super easy. The main downside is that you're are increasing your devops load. Getting up to speed with tools for imaging/installing, monitoring, load balancing, scaling, etc becomes increasingly important as you add services in this fashion.
As Servoy continues to fall behind the tech curve I think this approach is going to be important for keeping current Servoy installations running.