System Design

From caching to designing Twitter — learn how real-world systems are built, step by step.

Fundamentals
What is System Design?
The blueprint behind every app you use
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Scalability
From one user to one billion — how systems grow
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Load Balancing
Sharing the work so no server burns out
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Caching
Keep the good stuff close — skip the slow trip
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Databases: SQL vs NoSQL
Choosing the right home for your data
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Building Blocks
CAP Theorem
You can't have it all — pick two out of three
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Consistent Hashing
Adding a server shouldn't reshuffle everything
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Message Queues
Don't do everything right now — put it in line
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API Design
The contract between your system and the world
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Content Delivery Networks
Serve content from the closest shelf, not the warehouse
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Real-World Systems
Design a URL Shortener
Turn long links into tiny ones — at scale
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Design a Rate Limiter
Stop the flood before it drowns your servers
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Design a Chat System
Real-time messaging for millions — delivered instantly
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Design a Notification System
The right message, to the right person, at the right time
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Design a News Feed
Delivering personalized content to millions — instantly
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