System design interviews

Design systems. Pass interviews.

Interactive exercises that make you design real systems. Practice trade-offs, scaling decisions, and architecture patterns before the whiteboard.

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Real architecture problems

Design URL shorteners, chat systems, and notification pipelines. Each exercise mirrors what interviewers actually ask.

Trade-offs, tested

Every design decision has trade-offs. The exercises test whether you understand them, not whether you memorized a diagram.

Instant feedback on your reasoning

Know immediately whether your design holds up. Structured feedback on each decision, not a vague "looks good."

System Design + SOLID + DRY

Architecture thinking for interviews and production.

Try a Lesson

Write code from lesson one

Every lesson is an exercise you solve in your browser. Real code, real tests, real feedback.

Write a greeting function

main.ts

function greet(name: string) {

return `Hello, ${name}!`

}

Structured progression

Each concept builds on the last. You always know what to learn next.

Multiple exercise types

Quizzes, fill-in-the-blank, matching, and code keep every lesson engaging.

Instant feedback

Submit your answer and see test results in milliseconds.

Learn by doing

Solve exercises in your browser from the first lesson.

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Join over 5,000 learners

Flutter Zero to Mastery

Explore our courses

Pick a course and solve your first exercise.

Programming And Computers

Learn the principles of how programming and computers work.

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TypeScript

Learn TypeScript from variables to generics, with coding challenges you solve directly in your browser.

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Electricity and Current

Learn how electricity works, from voltage, current, and resistance to circuits, Ohm's law, and common components like resistors, LEDs, and capacitors.

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Microcontrollers

From GPIO pins and breadboard circuits to sensors, displays, motors, and communication protocols like I2C, SPI, and UART.

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System Design

Learn how APIs, databases, caching, and load balancing fit together to build scalable systems.

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Dart

An interactive Dart course where you code, test, and build apps directly in your browser.

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Flutter

An interactive Flutter course where you code, test, and build apps directly in your browser.

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S.O.L.I.D Principles in OOP

Learn the principles of how software should be structured, so you can guide AI to build better systems.

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D.R.Y. (Don't Repeat Yourself)

Learn to identify and eliminate code duplication, making your codebase cleaner and easier to maintain.

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Interactive courses

Every lesson is an exercise with instant feedback.

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Stop memorizing diagrams. Start designing.

Interactive system design exercises with instant feedback.

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