System Design Framework

The 4-Step Process

Every system design follows this structure. Skipping steps is the top mistake.

Step 1: Understand the Problem and Establish Design Scope (3-10 min)

Narrow an impossibly broad question into a tractable problem.

Ask about: users and scale | most important features | read/write ratio | non-functional requirements (latency, availability, consistency) | existing infrastructure | special constraints (mobile-first, offline, regulatory)

Produce: functional requirements (3-5 bullets) | non-functional requirements (scale, latency, availability, consistency model) | capacity estimation (QPS, storage, bandwidth)

Red flags if skipped: designing a system nobody asked for | over-engineering for imaginary scale | missing critical constraints (GDPR, real-time)

Step 2: Propose High-Level Design and Get Buy-In (10-15 min)

Sketch the big picture. Validate before diving deep.