High Level Design (HLD) understanding with example (Part1).

Designing a high-level design (HLD) for a software requires a broad understanding of the system’s architecture, functionality, and requirements. Here are some key things to consider when designing an HLD for a software:

HLD Breakdown: Image Ref: softwaredominos

1. Understand the system requirements: Start by understanding the requirements of the system. This involves identifying the problem that the system is trying to solve, the stakeholders who will use the system, and the features that the system must have.
2. Identify the major components: Identify the major components of the system and how they interact with each other. This involves defining the system architecture, which includes the major modules or subsystems and how they are connected.
3. Define the data model: Define the data model for the system, which includes the types of data that the system will store, how the data will be organized, and how the data will be accessed and manipulated.
4. Consider the system’s scalability: Consider the scalability of the system, which involves how the system will handle increasing levels of data and users over time. This includes defining the system’s capacity requirements and designing the system to handle future growth.
5. Consider the system’s security: Consider the security of the system, which involves identifying potential security risks and designing the system to protect against them. This includes defining access controls, authentication mechanisms, and encryption requirements.
6. Consider the system’s performance: Consider the performance of the system, which involves identifying potential bottlenecks and designing the system to perform efficiently. This includes defining the system’s response time requirements, throughput requirements, and load balancing mechanisms.
7. Identify third-party components: Identify any third-party components that the system will use, such as APIs, libraries, and frameworks. This includes defining the integration points for these components and ensuring that they meet the system’s requirements.
8. Create high-level architecture diagrams: Create high-level architecture diagrams that depict the major components of the system and how they interact with each other. This will help stakeholders understand the overall structure and functionality of the system.

Overall, designing an HLD for a software requires a deep understanding of the system’s requirements and how its components will work together to solve the problem at hand. By considering scalability, security, performance, and other factors, you can design a system that meets the needs of its users and stakeholders.

High-level design (HLD) diagrams are visual representations of the system architecture and major components of a software system. They are typically used to provide an overview of the system’s structure and functionality and are useful for communicating with stakeholders and developers.

Here are some common types of HLD diagrams:

1. Block diagrams: Block diagrams are used to depict the major components of the system and how they interact with each other. Each component is represented as a block, and the connections between the blocks show how they communicate with each other. For example, a block diagram for an e-commerce website might include blocks for the web server, application server, and database server, with arrows indicating the flow of data between them.
2. Data flow diagrams: Data flow diagrams (DFDs) are used to show how data moves through the system. They are particularly useful for showing how data is processed and transformed by different components of the system. In a DFD, data is represented as a flow, with arrows showing how it moves through the system. For example, a DFD for an e-commerce website might show how product data is entered into the system, stored in the database, and displayed to users.
3. Use case diagrams: Use case diagrams are used to show how users interact with the system. They are particularly useful for showing the system’s functionality from the perspective of the user. In a use case diagram, each use case (i.e. a specific interaction that a user can have with the system) is represented as an oval, with actors (i.e. users or other systems) represented as stick figures. For example, a use case diagram for an e-commerce website might include use cases for searching for products, adding products to a shopping cart, and checking out.
4. Sequence diagrams: Sequence diagrams are used to show the interactions between different components of the system over time. They are particularly useful for showing the flow of data and control between different components of the system. In a sequence diagram, each component is represented as a rectangle, with arrows showing the flow of control and data between them. For example, a sequence diagram for an e-commerce website might show how a user’s request to purchase a product is processed by the web server, application server, and database server.

Overall, HLD diagrams are a powerful tool for communicating the structure and functionality of a software system. By using different types of diagrams, you can provide a comprehensive overview of the system from different perspectives, helping stakeholders and developers understand the system’s architecture and behavior.

Here is one example of high-level design (HLD) and its real-world application:

Yulu bike-sharing platform:

2. User mobile app: The Yulu mobile app allows users to find and rent bikes, as well as manage their accounts and payments. The app has several features, including:

• Bike map: This shows the locations of bike stations and the availability of bikes at each station.
• Bike rental: Users can reserve a bike using the app, which will hold the bike for a set amount of time until the user arrives to pick it up. The user can then unlock the bike using a QR code or Bluetooth connection.
• Payment: The app allows users to add payment details and pay for their rentals using a credit or debit card.
• Account management: Users can manage their account settings, view their rental history, and access support through the app.

2. Bike stations: Yulu has designated bike stations throughout the city, where users can pick up and drop off bikes. Each station has a physical bike rack with designated spots for the bikes, as well as a kiosk with a touchscreen display that shows the station map and bike availability.

3. IoT-enabled bikes: Yulu bikes are equipped with IoT sensors that allow users to unlock the bike and track its location. The bikes have several features, including:

• QR code lock: The bike has a QR code that users can scan using the Yulu app to unlock the bike.
• Bluetooth lock: The bike can also be unlocked using a Bluetooth connection to the user’s smartphone.
• GPS tracking: The bike has a GPS sensor that allows Yulu to track its location and ensure that it is returned to a designated bike station.
• Battery and diagnostics: The bike has a battery and sensors that can detect any issues with the bike’s performance, such as low tire pressure or a malfunctioning brake.

4. Payment gateway: Yulu uses a payment gateway to process transactions for bike rentals. The payment gateway securely stores users’ payment information and processes transactions in real-time.

5. Maintenance and operations: Yulu manages bike maintenance, repair, and cleaning, as well as the operation of bike stations. This includes:

• Routine maintenance: Yulu performs regular maintenance on the bikes, such as checking the brakes, tires, and chain.
• Repair: If a bike is damaged or needs repair, Yulu will take it out of service and perform the necessary repairs.
• Cleaning: Yulu cleans the bikes regularly to ensure that they are sanitary and in good condition.
• Bike station management: Yulu manages the placement and availability of bikes at each station, as well as the kiosks and other infrastructure at the stations.

6. Analytics and data: Yulu collects data on bike usage and user behavior, which is used to optimize bike placement and improve the user experience. The data includes:

• Bike usage: Yulu tracks the number of rentals, duration of rentals, and popular bike stations.
• User behavior: Yulu collects data on user demographics, rental history, and feedback.

HLD diagrams will be covered in details in next article.

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