Upstream proxying means that Cloudsmith acts as a single point of contact for all Maven packages or dependencies, simplifying the process of integrating third-party packages into development processes. This process is transparent and controllable to the customer, allowing them to determine which repositories to check first and what actions to take in case of upstream failure. Caching takes it a step further by storing dependencies within Cloudsmith's environment, providing guaranteed great performance, control over package scanning and monitoring, and the ability to define when to look for new versions of packages. These features aim to make development and deployment processes more reliable and simple.