Design a URL shortener.

A common System Design interview question on System Design Basics. See the topic page for approach and related questions.

Design a rate limiter.

A common System Design interview question on System Design Basics. See the topic page for approach and related questions.

How would you scale a read-heavy service?

A common System Design interview question on System Design Basics. See the topic page for approach and related questions.

SQL vs NoSQL for this use case — which and why?

A common System Design interview question on System Design Basics. See the topic page for approach and related questions.

Where would you add a cache and what would you cache?

A common System Design interview question on System Design Basics. See the topic page for approach and related questions.

System Design · INTERVIEW & OA PREP

Topic 10 of 12

System Design Basics

Even for internships and new grads, a light system-design or HLD discussion is increasingly common. You're not expected to design Google — you're expected to reason about scale, trade-offs, and components clearly.

Key concepts

Clarify requirements and scale first (users, reads vs writes, latency).
Building blocks: load balancer, cache, database, queue, CDN.
SQL vs NoSQL trade-offs; when to denormalize.
Caching, sharding, and replication for scale.

Questions that get asked

Design a URL shortener.
Design a rate limiter.
How would you scale a read-heavy service?
SQL vs NoSQL for this use case — which and why?
Where would you add a cache and what would you cache?

Tip

Drive the conversation: state assumptions, sketch the high-level boxes, then go deep only where the interviewer probes.

Common mistake

Jumping to components before clarifying scale. 'How many users?' should be your first question, not your last.

Quick checks

Three tap-only questions to test your recall on this topic.

Keep going

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