Introduction

System design is the process of creating a system that performs a function under a defined set of constraints.

Example: "Design a URL shortener that can handle millions of requests per day, stay highly available, and remain performant."

These questions are intentionally open-ended. Interviewers use them to understand how you think, how you communicate, and whether you understand the fundamentals of building scalable distributed systems.

System design varies depending on the role you’re interviewing for, but in this series, we’ll focus primarily on backend engineering system design.

These questions typically involve designing large-scale distributed systems (feeds, messaging systems, load balancers, event-driven pipelines, queues, etc.) that serve a lot of users and need to be:

• Scalable
• Reliable
• Performant

There are three main reasons engineers should learn system design:

Interviews are more competitive than ever. Most companies, not just big tech, expect engineers to have at least a basic grasp of system design fundamentals.

LeetCode helps you pass interviews, but system design helps you ship real products.

Understanding networking, storage, queues, APIs, scaling, and reliability makes you better at diagnosing problems and designing solutions, regardless of what company you work at. Every engineer benefits from knowing how to architect a system around real constraints like user count, budget, latency, or timeline.

Most of us didn’t become engineers solely for the paycheck; we enjoy building things and solving problems. Depending on your job, you may never get the chance to design infrastructure from scratch. System design fills that gap.

Think about it this way: LeetCode exists because developers needed a place to practice solving data structure and algorithm problems, not just read about them.

So where’s the equivalent for System Design?

Sure, you can learn the fundamentals (CAP theorem, replication, queues, caching) or watch YouTube videos. But where do you actually practice system design problems you've never seen before, without being hand-held by a tutorial that ruins the challenge?

You can learn the concepts anywhere; the fundamentals are the same across books and courses. But only this tool lets you apply that knowledge in a structured, repeatable way.

With SystemDesignSandbox, you can:

• Get a fresh system design prompt
• Walk through each stage of your design
• Get feedback on every step
• Understand what’s missing and correct your approach
• Converge on a solution that would actually pass in an interview

It turns system design from something you study into something you can practice. Just like LeetCode, but for real-world, large-scale systems.