As a first, easy to understand, approach, GeneXus Cloud Deployment Services architecture consists of 3 components: Its GeneXus Cloud Tools, GeneXus Cloud Manager and GeneXus Cloud Unit.
They provide GeneXus with the ability to communicate with GeneXus Cloud Manager to deploy applications on the cloud and upgrade them as necessary.
It allows managing the various GeneXus Cloud Units where applications are published. Also, it provides an administration console and traceability features for all deployment activities.
It's the cloud infrastructure or platform unit where applications are published. Various sizes and vendors are available for the customer to choose from: Amazon, Google, IBM SoftLayer, Montevideo COMM, Microsoft.

Going deeper, there is more under the hood, third party tools and services are used
- GXcloud Tools use Amazon S3 Services to upload deploys to GXcloud Manager
- Each deploy is stored using GIT version control system, GXcloud Units get the (new) versions of the binaries from there.
- Depending your plan, Amazon S3 Services store backups
Read more details at GeneXus Cloud Tools, GeneXus Cloud Manager and GeneXus Cloud Unit.