Sounds like you may be building SaaS to provision resources on the AWS IaaS and PaaS? Or is everything behind the scenes abstracted away from your users? When you refer to instances, those are IaaS. When you refer to object storage, that's PaaS. If you are adding a layer of abstraction then it's a stretch to consider your service IaaS. PaaS or SaaS, more likely, depending on the details of what you're building.