Getting Started with System Design Interviews

A practical guide to approaching system design interviews at top tech companies. Learn the framework, key concepts, and common pitfalls.

June 15, 20258 min read

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Getting Started with System Design Interviews#

System design interviews are one of the most challenging parts of the software engineering interview process. Unlike coding interviews, there is no single correct answer — instead, interviewers evaluate your ability to think through trade-offs and design scalable systems.

The STAR Framework for System Design#

When approaching a system design problem, use this structured approach:

Scope — Clarify requirements and constraints
Think — Brainstorm components and their interactions
Architect — Draw the high-level design
Refine — Dive deep into bottlenecks and trade-offs

Key Concepts to Master#

CAP Theorem#

The CAP theorem states that a distributed system can only guarantee two of three properties: Consistency, Availability, and Partition Tolerance.

Horizontal vs. Vertical Scaling#

Vertical scaling: Add more power to existing machines (CPU, RAM)
Horizontal scaling: Add more machines to distribute the load

Caching Strategies#

Cache-aside (lazy loading)
Write-through
Write-behind
Refresh-ahead

Common System Design Interview Topics#

Design a URL shortener (like Bit.ly)
Design a social media feed
Design a distributed message queue
Design a rate limiter
Design a CDN

Tips for Success#

Always start by clarifying requirements
Make reasonable assumptions and state them explicitly
Start with a simple design and iterate
Discuss trade-offs for every major decision
Think about failure scenarios and how to handle them