ORM

Object-Relational Mapping

Library that maps database tables to application objects.

When you'd see it: Software development, when application code talks to a relational database without writing raw SQL.

Why it matters: An ORM lets developers work with database rows as objects in their programming language. It speeds development but can hide inefficient queries, which is a common source of performance problems.

Common mistakes: Trusting the ORM blindly. Convenient ORM code can fire dozens of hidden queries (the N+1 problem) that quietly wreck performance.