What are key features of the build system's architecture regarding storage classes?

The option noting that as artifacts get older, they move through various storage classes to limit retention costs is a valid statement about the build system's architecture. This process is commonly referred to as object lifecycle management in cloud storage systems. By strategically transitioning artifacts to lower-cost storage classes over time, organizations can manage storage costs effectively and optimize resource allocation.

In the context of Google Cloud Storage, there are several storage classes tailored for different access frequencies and retention needs. For instance, Nearline and Coldline storage classes are designed for infrequently accessed data, providing significant cost savings for older artifacts that are no longer in regular use but still need to be retained for compliance or reference.

This approach not only helps in cost management but also maintains organizational efficiency, as it automatically adjusts the storage strategy based on the age and usage patterns of the artifacts without requiring manual intervention.

The other options provide different aspects of build systems and storage but do not capture the essence of optimizing costs through storage class transitions as directly as the correct option does.