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In the world of software engineering and complex systems, designing well is just as important as writing code. This is where HLD – High Level Design comes into play, which is the high-level design of a system. HLD represents a fundamental phase of the development cycle because it defines how a system will function before diving into implementation details.
What is HLD (High Level Design)
High Level Design is an architectural description of the system that provides an overview of the solution. In this phase, we don't talk about code, specific algorithms, or detailed data structures, but rather about:
- main components of the system
- responsibilities of each component
- interactions between various modules
- data and control flows
- technologies or platforms involved (at a conceptual level)
❇️ The goal of HLD is to answer the question:
“How will the system be structured to satisfy the requirements?”
What is HLD for?
HLD plays a key role for several reasons:
- Alignment among stakeholders 🔄️
It provides a common vision for developers, architects, project managers, and clients, reducing misunderstandings and ambiguity. - Risk reduction ⤵️
Identifying architectural problems during the design phase is much less expensive than correcting them after implementation. - Basis for Low Level Design (LLD) 🔰
HLD is the starting point for Low Level Design, which will delve into technical and implementation details. - Support for planning 🚩
It helps in estimating time, costs, dependencies, and workloads. - Maintainability and scalability 👷♂️
A good high-level design makes the system easier to evolve and maintain over time.
How an High Level Design is created
Creating an HLD generally follows a few key steps.
1. Requirements analysis
It starts from functional and non-functional requirements (performance, security, scalability, reliability). The HLD must demonstrate that the chosen architecture is capable of satisfying them.
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2. Definition of the architecture
The most suitable architectural style is chosen, for example:
- layered architecture
- microservices
- client-server
- event-driven
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3. Identification of main components
For each component, the following are defined:
- responsibilities
- inputs and outputs
- interactions with other components
Implementation details are not yet addressed.
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4. Diagrams and visual representations
HLD is often accompanied by diagrams, such as:
- architecture diagrams
- component diagrams
- data flow diagrams
These tools help make the design more understandable and sharable.
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5. High-level technology choices
Technologies, frameworks, or infrastructures can be indicated in a non-binding way, for example:
- relational database vs NoSQL
- synchronous vs asynchronous communication
- cloud vs on-premise
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6. Documentation
Finally, the HLD is formalized in a document describing:
- system overview
- proposed architecture
- assumptions and constraints
- risks and open considerations
| HLD - Final Architecture |
Conclusion
High Level Design is not just a document, but a strategic tool that guides the entire development of the system. Investing time in its creation means building solid foundations, reducing future errors, and improving the overall quality of the product. In short, a good HLD is the first step toward well-designed software.
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