Before designing any system, you must understand what you are building and why you are building it. Misunderstood requirements can lead to overengineering, wasted effort, or an unusable product.

If I had an hour to solve a problem, I would spend 55 minutes thinking about the problem and 5 minutes on the solution — Einstein.

Two Types of Requirements

1️⃣ Functional Requirements (FR)

These describe what the system should do – the features and operations.

Examples:

• Users can upload and share photos.
• The system sends email notifications.
• Users can search for other users by username.

2️⃣ Non-Functional Requirements (NFR)

These describe how well the system performs under certain conditions.

Examples:

• System must handle 10,000 concurrent users
• API should respond within 200ms
• Availability should be 99.99%
• Data should be encrypted in transit

Steps to Understand Requirements

Step 1: Clarify the Objective

Ask:

• What is the purpose of the system?
• Who are the users?
• What is the main business value?

Step 2: Define the Core Features (Functional Requirements)

List the primary operations your system must support.

What are the must-have user flows?

Step 3: Identify Non-Functional Requirements (Performance, Security, Scale)

Ask:

• How many users will be using this?
• What is the expected request volume?
• Is it real-time or eventual?
• What are the SLAs (Service Level Agreements)?

Step 4: Understand Constraints

These could be:

• Technology limitations (e.g., must use MySQL)
• Compliance rules (e.g., GDPR)
• Budget or timeline