backend · easy
Active Record
Rails ORM: a class per table, instances per rows, with migrations, validations, and associations.
Where you see it
Active Record is the Rails flavor of ORM. You still need SQL for joins, indexes, and N+1 debugging — Learn SQL and Arena PostgreSQL cover that; here you learn the object mapping.
Why it matters
Almost every Rails job is an Active Record job. Interviewers probe `belongs_to`/`has_many`, callbacks, and whether you know when to drop to SQL.
Tags: rails, sql