- System Analysis and Design - Home
- System Analysis & Design - Overview
- Differences between System Analysis and System Design
- System Analysis and Design - Communication Protocols
- Horizontal and Vertical Scaling in System Design
- Capacity Estimation in Systems Design
- Roles of Web Server and Proxies in Designing Systems
- Clustering and Load Balancing
- System Development Life Cycle
- System Analysis and Design - Requirement Determination
- System Analysis and Design - Systems Implementation
- System Analysis and Design - System Planning
- System Analysis and Design - Structured Analysis
- System Design
- System Analysis and Design - Design Strategies
- System Analysis and Design - Software Deployment
- Software Deployment Example Using Docker
- Functional Vs. Non-functional Requirements
- Data Flow Diagrams(DFD)
- Data Flow Diagram - What It Is?
- Data Flow Diagram - Types and Components
- Data Flow Diagram - Development
- Data Flow Diagram - Balancing
- Data Flow Diagram - Decomposition
- Databases in System Design
- System Design - Databases
- System Design - Database Sharding
- System Design - Database Replication
- System Design - Database Federation
- System Design - Designing Authentication System
- Database Design Vs. Database Architecture
- Database Federation Vs. Database Sharding
- High Level Design(HLD)
- System Design - High Level Design
- System Design - Availability
- System Design - Consistency
- System Design - Reliability
- System Design - CAP Theorem
- System Design - API Gateway
- Low Level Design(LLD)
- System Design - Low Level Design
- System Design - Authentication Vs. Authorization
- System Design - Performance Optimization Techniques
- System Design - Containerization Architecture
- System Design - Modularity and Interfaces
- System Design - CI/CD Pipelines
- System Design - Data Partitioning Techniques
- System Design - Essential Security Measures
- System Implementation
- Input / Output & Forms Design
- Testing and Quality Assurance
- Implementation & Maintenance
- System Security and Audit
- Object-Oriented Approach
- System Analysis & Design Resources
- Quick Guide
- Useful Resources
- Discussion
System Design - Low Level Design
Introduction
In system design, the focus is often split into two main areas: High-Level Design (HLD), which outlines the system's architecture and overall structure, and Low-Level Design (LLD), which delves into the detailed blueprint of the system. While HLD provides a bird's-eye view, LLD offers a zoomed-in perspective, focusing on individual components and their interactions.
This article explores the concept of Low-Level Design, its importance, and the steps involved in crafting it. It also highlights principles, challenges, and best practices to build robust and maintainable systems.
What is Low-Level Design (LLD)?
Low-Level Design refers to the process of designing the internal workings of individual components in a software system. It breaks down the abstract architectural ideas from HLD into concrete, implementable details.
Key characteristics of LLD
Detailed documentation of classes, methods, and interactions.
Definitions of how system components communicate internally.
Inclusion of diagrams like UML (Unified Modeling Language) to represent relationships and workflows.
LLD is typically created after HLD and is meant for developers who will implement the system. It bridges the gap between system architecture and actual code.
Importance of Low-Level Design in System Design
Bridges the Gap Between HLD and Code− LLD acts as a guideline for developers to implement the high-level architecture in code.
Improves Code Quality− By defining relationships, dependencies, and workflows beforehand, LLD ensures that the codebase adheres to design principles, making it maintainable and efficient.
Reduces Development Errors− With detailed specifications in place, developers are less likely to misinterpret the system requirements.
Facilitates Team Collaboration− LLD provides a common language (diagrams, patterns, and principles) for teams to discuss and refine system behavior.
Supports Testing and Debugging− A well-structured LLD makes it easier to identify and resolve issues during testing.
Key Components of Low-Level Design
To create an effective LLD, designers use various components, each serving a specific purpose in illustrating system details.
Class Diagrams
Show the relationships between classes, their attributes, and methods.
Provide a blueprint for object-oriented implementation.
Include associations like inheritance, composition, and aggregation.
Example: A class diagram for an e-commerce system may depict classes like Product, Order, Customer, and their relationships.
Sequence Diagrams
Illustrate how objects interact in a sequence of events.
Useful for understanding the flow of a specific use case.
Represent objects, messages, and lifelines.
Example A sequence diagram for the "Add to Cart" feature in an online store might detail how the User, Cart, and Inventory classes interact.
Activity Diagrams
Represent the workflow of a system process.
Highlight decision points and actions in a process.
Example An activity diagram for a login feature might show:
User inputting credentials.
System validating credentials.
Login success or failure.
State Diagrams
Capture the state transitions of an object over time.
Useful for systems with complex states (e.g., order states in e-commerce).
Example An order might transition through states like:
Created → Processed → Shipped → Delivered.
Low-Level Design Principles
Low-Level Design relies on several principles to ensure the resulting system is clean, maintainable, and scalable.
SOLID Principles
Single Responsibility− A class should have one and only one reason to change.
Open/Closed− Classes should be open for extension but closed for modification.
Liskov Substitution− Subtypes must be substitutable for their base types.
Interface Segregation− Interfaces should be specific to the client.
Dependency Inversion− High-level modules should not depend on low-level modules.
Design Patterns
Design patterns are reusable solutions to common problems in software design. Examples include−
Creational Patterns− Singleton, Factory.
Structural Patterns− Adapter, Decorator.
Behavioral Patterns− Observer, Strategy.
Dependency Injection
This principle encourages loosely coupled code by injecting dependencies rather than hardcoding them.
Steps to Create a Low-Level Design
Understand Requirements− Analyze use cases and break them into smaller tasks.
Identify Components− Determine the classes, interfaces, and methods needed.
Define Relationships− Establish associations like inheritance and composition.
Design Workflows− Create sequence and activity diagrams for key workflows.
Document Details− Include method signatures, input/output parameters, and pseudocode.
Review and Refine− Ensure the design adheres to principles and patterns.
Example of Low-Level Design
Consider a Library Management System. One feature is "Borrow a Book."
Class Diagram
Classes− User, Book, BorrowTransaction.
Relationships−
User borrows a Book.
BorrowTransaction keeps track of borrow details.
Relationships
User can borrow multiple Books.
A BorrowTransaction records which User borrowed which Book.
Sequence Diagram
User requests to borrow a book.
System checks book availability.
System creates a transaction record.
Steps
User requests to borrow a book.
LibrarySystem checks book availability.
If available, LibrarySystem creates a BorrowTransaction.
LibrarySystem confirms the borrowing and notifies the User.
Best Practices in Low-Level Design
Follow Design Principles− Adhere to SOLID principles and use design patterns judiciously.
Document Extensively− Ensure all details are clear for developers to implement.
Ensure Scalability− Design for future growth by anticipating changes.
Minimize Coupling− Reduce dependencies between components to improve maintainability.
Peer Review− Collaborate with teammates to validate the design.
Challenges in Low-Level Design
Over-Engineering− Adding unnecessary complexity can hinder development.
Time Constraints− Detailed LLDs can take time, especially for large systems.
Evolving Requirements− Frequent changes can render designs obsolete.
Skill Dependency− LLD creation requires experienced designers who understand design principles.
Conclusion
Low-Level Design is a critical phase in system design that translates architectural blueprints into actionable plans for development. By focusing on classes, workflows, and design principles, it ensures a robust and maintainable codebase. Although challenging, investing in detailed LLD saves time and resources during development and maintenance, making it an essential skill for system designers and developers.