Why does the wca4z transformation approach recommend exposing generated Java services through an API gateway?

Think of it like working hands-on with IBM mainframe systems — the answer here is 'An API gateway provides routing, security, and versioning so COBOL callers and new consumers can reach the Java service through a stable endpoint'. An API gateway provides a stable, versioned entry point with authentication and routing, allowing both legacy COBOL callers and new Java consumers to reach the generated service without depending on i. On real mainframe exams, this concept comes up repeatedly so make sure you have it locked in.