Low-Level Design Foundations

Extract functional requirements, constraints, and likely change points from an LLD interview prompt.

Classify domain concepts as entities, value objects, or services.

Define invariants that keep a domain model in a valid state.

Assign object responsibilities to maximize cohesion and minimize coupling.

Choose between composition and inheritance for a stated design problem.

Specify clear contracts for classes and interfaces.

Draw a UML class diagram for a small object-oriented design.

Trace one use case with a UML sequence diagram.