PostgreSQL 1 story

PostgreSQL sits inside Database Engines & Architecture as a distinct technical layer, with its own setup, compatibility, and workflow considerations. Coverage uses PostgreSQL, PostgreSQL architecture, PostgreSQL platform, and PostgreSQL configuration to explain how the layer works, what it depends on, and where compatibility or configuration matters. This keeps PostgreSQL narrower than Database Engines & Architecture as a whole while giving readers enough context to compare approaches, understand expected behavior, and recognize when a problem-specific tag is the better fit.