In an Apex REST class, what keyword is used to indicate that the class is globally accessible?

In Apex, the keyword used to indicate that a class is globally accessible is "global." This means that the class can be accessed by all other Apex code, regardless of whether it is within the same namespace or a different one. This level of accessibility is particularly important when developing managed packages, as it allows external systems and applications to interact with your Apex code seamlessly.

Using the "global" modifier is essential for classes that are intended to be part of a public API, as it ensures that users in other organizations or namespaces can utilize the functionality provided by the class. In the context of Apex REST classes, making them global enables external systems to invoke the REST services exposed by these classes, facilitating integration scenarios.

In contrast, other access modifiers such as "public," "private," and "internal" offer different levels of accessibility, but they do not enable inter-namespace accessibility to the same extent as "global." Public classes can be accessed from within the same namespace and would work for shared functionality in the same organization but would not be accessible from other namespaces or organizations.