System Design Learning Platform

There are plenty of system design resources online. Blog posts, courses, YouTube videos. Most of them have the same problem: you read about an architecture, maybe look at a static diagram, nod along, and forget everything a week later.

Learning architecture is like learning to code. You have to do it, not just read about it.

The Codelit blog has 80 interactive system design articles. Each one pairs a written explanation with an interactive diagram you can manipulate, audit, and modify. It's learning by doing.

Every article includes an embedded Codelit canvas. When the article says "the API gateway routes requests to the appropriate microservice," you can click the API gateway node, see its connections, and understand how it fits in the system.

When it says "adding a cache layer between the API and database reduces latency by 10x," you can actually add the cache node to the diagram and see how it changes the data flow.

This isn't a gimmick. I never remembered a system-design article I only read. The ones that stuck were the ones I had to modify. Manipulating a diagram while reading about it builds a stronger mental model than staring at a static picture.

Click any node in an article's diagram and the explain panel opens with context specific to that article's topic. If you're reading about microservices and click the message queue, the explanation covers why queues matter in a microservice architecture, not a generic "what is a message queue" definition.

The explanations are layered. First: what this component does. Second: why it's in this specific architecture. Third: what would happen if you removed it. Fourth: alternatives you could use instead.

Some articles include challenge prompts. After reading about a topic, you get a prompt like:

• "This architecture handles 1,000 requests/second. Modify it to handle 100,000."
• "The current design has a single point of failure. Find it and fix it."
• "Add GDPR-compliant data handling to this system."

Your modifications are compared against a reference solution. Not for a grade, since there's no single right answer in architecture, but to show you approaches you might not have considered.

The articles cover the full spectrum of system design:

Fundamentals (20 articles). Load balancing, caching strategies, database sharding, message queues, API design, CDNs, DNS, rate limiting, circuit breakers, consensus algorithms. Each one goes deep enough to be useful in a real design discussion.

Patterns (20 articles). Event-driven architecture, CQRS, saga pattern, bulkhead pattern, strangler fig migration, sidecar pattern, ambassador pattern, backend for frontend, database per service, shared database. Each pattern includes when to use it, when not to use it, and real-world examples.

Real-World Systems (20 articles). How Netflix streams video, how Uber matches riders, how Stripe processes payments, how Discord handles millions of concurrent users. These pair with the company architecture templates in the template library.

Infrastructure (10 articles). Container orchestration, service mesh, observability, CI/CD pipelines, infrastructure as code, multi-region deployment, disaster recovery, blue-green deployments, canary releases, feature flags.

Interview Prep (10 articles). Structured approaches to system design interviews. How to estimate scale, how to identify requirements, how to present trade-offs, how to handle follow-up questions. Based on what actually gets asked in real system-design interviews.

The articles aren't just static text with embedded diagrams. The AI layer means you can ask questions and get architecture-specific answers.

Reading about caching? Ask: "What happens if I use write-through instead of write-behind for this system?" The AI modifies the diagram to show the difference and explains the trade-offs in context.

Reading about database sharding? Ask: "Show me what happens when I shard by user_id vs. by geography." The AI generates both versions side by side.

This turns passive reading into active experimentation. You're not just learning that write-through caching exists. You're seeing how it changes the specific architecture you're studying.

Based on analytics:

• 40% interview prep. Engineers preparing for system design interviews at tech companies
• 30% learning. Developers expanding their architecture knowledge
• 20% teaching. Senior engineers sharing articles with junior team members
• 10% reference. Architects looking up specific patterns during design work

The interview prep crowd is the most engaged. Average session time is 28 minutes, which is long for a blog. They're not skimming; they're working through the diagrams.

Browse all 80 articles at codelit.io/blog. Pick a topic that interests you or that you know you'll be asked about in an upcoming interview. Open the diagram, click around, modify things, break things.

That's how you learn architecture. Not by reading about it. By building it.