Low-Level Design (LLD)

About

Low-Level Design, also known as detailed design or micro-level design, provides detailed information about the system's components and their interactions. It focuses on the internal structure and workings of the system.

LLD is like the detailed floor plan of the building. It goes into the specifics of each room, the layout of furniture, wiring, plumbing, etc.

Key Aspects

1. Class Diagrams: Defines the classes, their attributes, methods, and relationships.

2. Sequence Diagrams: Describes the sequence of interactions between different components for specific use cases.

3. Data Structures: Specifies the data structures to be used and their organization.

4. Algorithms: Details the algorithms to be implemented and their logic.

5. Component Design: Provides detailed design of individual components and modules.

6. Database Design: Describes the database schema, including tables, relationships, and indexes.

Purpose

• Provides a detailed design specification for developers to implement the system.

• Ensures that all components and modules are well-defined and their interactions are clear.

• Serves as a guide for writing code and unit tests.

Example of a web-based e-commerce application

Class Diagram:

• User class with attributes (userId, userName, password) and methods (login(), register()).

• Product class with attributes (productId, productName, price) and methods (getProductDetails()).

Sequence Diagram:

• Sequence for user login: User enters credentials -> System validates credentials -> System fetches user data -> User is logged in.

Data Structures:

• User: HashMap to store user sessions.

• Product: ArrayList to store product details.

Algorithms:

• Search algorithm for product catalog using binary search.

Component Design:

• Detailed design of the Shopping Cart component, including methods for adding, removing, and updating items.

Database Design:

• User table with columns (userId, userName, password).

• Product table with columns (productId, productName, price).