LLD — Low Level Design

Low-Level Design (LLD) is a detailed design phase in software development that follows the High-Level Design (HLD) stage. LLD focuses on transforming the high-level architectural design into a more granular and detailed design, specifying how each component or module will be implemented. Here are the key steps involved in LLD:

1. Understanding Requirements: Review the requirements and functional specifications to gain a clear understanding of the system’s expected behavior and functionality.
2. Decomposing Modules: Identify the major modules or components defined during the HLD phase and further decompose them into smaller, manageable units. This decomposition helps in defining the responsibilities and interactions of each module.
3. Defining Data Structures: Determine the data structures required by each module, including variables, objects, classes, and their relationships. This step involves defining the attributes, methods, and associations of each data structure.
4. Designing Algorithms: Define the algorithms and logic required to implement the desired functionality within each module. This includes specifying the step-by-step procedures, decision-making processes, and any computational operations.
5. Database Schema Design: Design the database schema if the system involves data persistence. Define the tables, relationships, and constraints required to store and retrieve data efficiently.
6. Interface Design: Design the interfaces between modules, specifying the inputs, outputs, and communication protocols. This includes defining function signatures, method parameters, return types, and error handling mechanisms.
7. Error Handling and Exception Handling: Identify potential errors and exceptions that can occur during the execution of the system. Define error handling mechanisms, such as exception handling, error codes, and error messages.
8. Security and Performance Considerations: Address security aspects, including data encryption, access control, authentication, and authorization. Additionally, consider performance optimizations, such as efficient algorithms, caching mechanisms, and resource utilization.
9. Documentation: Document the LLD artifacts, including detailed design documents, diagrams (e.g., class diagrams, sequence diagrams), and any relevant specifications. These documents serve as references for developers during the implementation phase and for future maintenance.

LLD aims to provide detailed guidelines for developers to implement each module/component. It focuses on the internal workings of the system, specifying the data structures, algorithms, interfaces, and other implementation details necessary for building the software. LLD helps ensure that the high-level design is accurately translated into a concrete and implementable solution.