Testing Admin tool for server set with AWS technology

Currently I'm trying to test Admin tool for server set with AWS technology. I did some exploratory, destructive and cross-browser tests on Admin tool, moreover I tested Api get requests for data and validated if the response returned by Api matches with Admin. Now I'm thinking about checking full Api list and perform some load tests with postman. So my question is what else can I do to better test this service. Maybe someone could recommend me some tools that I can use to cover all of the risk areas. Any help would be appreciated I have only one year of experience in testing from game-dev. Maybe some senior testers would like to give me some tips what I can do to deliver best quality. Thanks in advance!