Episode 3: Breaking Down Requirements – Ask First, Architect Later

From the YouTube Series: “High-Level System Design – A Simplified Guide” by TechSimplified by Rajdeep

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Goal of This Episode

Before you write a single line of architecture, you need clarity — clarity that comes from asking the right questions.

In this post, we’ll cover a 4-layered mental model that helps you break down even the most vague system design prompts (e.g., “Design Pastebin”) into clear, concrete, design-driving insights.

Whether you're preparing for FAANG-level interviews or designing real-world backend systems — this framework is your first weapon.

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4-Layered Thinking: A Systematic Approach

Here’s the model we’ll be using:

Layer 1: Functional Questions

“What should the system do?”

This includes user-facing actions (CRUD operations, sharing, search, etc.) and API-level capabilities. It answers what’s expected of the system — not how.

Example (Pastebin):

• Can users create/view/delete pastes?

• Can pastes expire?

• Should users be logged in or anonymous?

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Layer 2: Non-Functional Questions

“What shape does the system need to take to meet user expectations?”

These include latency, scalability, availability, and throughput constraints — i.e., the things that make your system fast, reliable, and production-grade.

Pastebin Examples:

• Creation should be instant → API should be synchronous and fast

• Millions of requests/day → Need a high-write scalable datastore

• Popular pastes need high availability → Use Redis/CDN caching

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Layer 3: Edge Cases & Constraints

“What are the hidden constraints or special conditions we must account for?”

This is where great design begins to stand out. These questions uncover:

• Input limits (e.g., paste size = 1MB)

• Abuse prevention (e.g., moderation needs)

• Legal/privacy concerns (e.g., audit logging, PII handling)

Pastebin Examples:

• No binary files → Use text-only schema

• Legal compliance → Add audit logs

• Abuse detection → Queue pastes for moderation

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Layer 4: UX & Product Flow

“How does the user interact with the system?”

This layer links product design and architecture — the more clearly you understand the flow, the better you can shape it technically.

Examples:

• Anonymous and logged-in flows → Optional auth middleware

• Editable pastes → Requires ID versioning

• Expiry logic → TTL index or background job

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How This Helps System Design?

Asking great questions leads to fewer assumptions and better architecture.

Each layer gives just enough clarity to choose the right tools, tradeoffs, and patterns.

Let’s connect this to some real architectural choices:

This mental model becomes the first page in your design — a structured breakdown that proves you understand the business, users, and constraints before proposing solutions.

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Watch the Episode

🎥 Watch Episode 3 – Breaking Down Requirements

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💬 Final Thoughts

In real-world engineering, asking the right questions is the design. This episode teaches you how to think like a senior engineer — not just pass an interview.

If you liked this guide, check out the full YouTube playlist:
➡️ High-Level System Design – A Simplified Guide

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