High Level Architecture Design Document

How to Create a High-Level Architecture Design Document

When starting a new IT project, one of the most important steps is creating a High-Level Design (HLD) document. An HLD describes how the system will be built in broad terms — without going too deep into technical configurations. Think of it as the blueprint that ensures everyone (from business teams to developers) understands the direction before diving into detailed work.

Why Do You Need an HLD?

An HLD provides:

• Clarity of purpose – explains what problem the solution is solving.

• Alignment – keeps business, development, and operations teams on the same page.

• Early risk management – identifies risks, assumptions, and dependencies upfront.

• Reusable structure – ensures consistent documentation across different projects.

Key Sections of an HLD Document

Here’s a simple structure you can follow:

1. Introduction

• Purpose: Why this design is being created.

• Key Benefits: What value the solution will bring.

• Scope: What is in and out of scope.

2. RAID (Risks, Assumptions, Issues, Dependencies)

• List potential risks.

• Note assumptions the design is based on.

• Capture known issues.

• Highlight external dependencies.

3. Constraints

• Standards or compliance requirements.

• Patterns or best practices that should be followed.

4. Functional Design

• Business Architecture: Process flows and steps.

• Data Architecture: Data elements, integrations, and handling of sensitive data.

• Application Architecture: Key application components and user experience.

• Technology Architecture: The big-picture view of systems, networks, and platforms.

5. Component Design

• List the major components (e.g., an application, database, cloud service).

• Provide an overview, design decisions, and rationale.

• Include diagrams to show how components fit together.

6. Non-Functional Design

Covers quality aspects such as:

• Backup and recovery strategy

• Availability and resilience

• Disaster recovery

• Performance and scalability

• Monitoring (operational and security)

• Security controls and compliance

7. Environments

Define the environments you’ll need:

• Development (DEV)

• Testing (SIT/UAT)

• Pre-production

• Production

8. Testing and Acceptance

List the testing types you plan to run, such as:

• Unit testing

• Integration testing

• User acceptance testing (UAT)

• Non-functional testing (security, performance, disaster recovery)

9. Bill of Materials

Summarize what’s required to implement the solution:

• Cloud services

• Hardware (if any)

• Software licenses

Tips for Writing an HLD

• Keep it simple – Don’t overload the document with technical jargon. Use diagrams wherever possible.

• Make it reusable – Stick to a template so you can apply it across projects.

• Highlight decisions – Document key design choices and explain why they were made.

• Collaborate – Involve architects, business analysts, developers, and testers early on.

Conclusion

A High-Level Design document bridges the gap between business needs and technical implementation. By following a structured approach, you make sure your project has a clear direction, reduces risks, and sets up a strong foundation for detailed design and implementation.