How to Create High Level Design Document

What is High Level Design (HLD)?

A High Level Design is created in the very initial phase of a project. An HLD explains the target architecture and its interfaces at a high level. The primary objective of HLD is to provide an overview of a system architecture including the components that are needed to be considered to develop the system.

A suitable HLD template for your IT organisation will help you quickly create High Level Design documents in a consistent way instead of thinking the table of contents for each project again and again.

In my view, a good HLD should have the following contents. However, it can be customised to meet specific requirement. At least this will give you a good starting point!

Inventory

An inventory of existing landscape must be created if the project impacts an existing system such as Upgrade or Migration projects.

Target Platform

You must identify the target platform, where the system will be hosted. Also, you must verify if the required resources are available on the target platform. Appropriate action needs to be taken in case of resource unavailability.

Solution Concept

The solution concept must be described at a high level. The solution concept must show the resources needed to host the system architecture.

High Level Design Diagram

A high level design diagram should be created to explain the target architecture and its primary networking interfaces.

Security

You must ensure the solution is security compliant. It’s a good practice to have a table in the HLD to show the security attributes those considered. Any exception must be called out with appropriate rationale.

Risk & Mitigation

Identify the risks to the project and capture the mitigation plan. Prioritise the risks and mark them accordingly. For example, unavailability of certain resource in the target platform can be a blocker to the project.

RACI Matrix

A RACI matrix should be created to clearly designate roles and responsibilities of all the teams associated to the project. It should also show all the stakeholders, who are impacted by the project.

Thanks for reading, give it a 👏 if you like it. Please leave a comment and let me know if you have any feedback.

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