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Complex topics, explained simply

Clear articles and structured courses on system design, microservices, databases, LLM internals, and AI engineering — built so you actually understand, not just memorize.

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9

Courses

76

Lessons

422

Articles

Not sure where to start?

Pick the path that matches your goal — every option is free and self-paced.

New to backend?

Follow the Backend Engineer path — databases, caching, messaging, and system design in order.

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Interview prep?

CAP theorem, load balancing, microservices patterns — everything you need for system design interviews.

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Prefer reading first?

Start with a popular comparison article — REST vs GraphQL vs gRPC, explained in plain language.

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Built for understanding, not buzzwords

Core Concept Learning is a free educational site for backend, system design, and AI engineering. Guides emphasize mechanisms, failure modes, and decision rules — with original diagrams you can study at your own pace. No signup wall. Corrections and topic ideas are welcome via contact; who we are and how we write is on About.

What's New

Latest articles and updates

New
Documentation MCP Servers: How Context7 Eliminates AI API Drift

One of the most persistent frustrations in AI-assisted development is API Drift. You ask an AI coding assistant to write…

12 min read

New
Gastown Architecture: Multi-Agent Factory vs Normal Sessions

Most multi-agent software engineering frameworks suffer from the same fatal flaw: they treat coding as a simulated conve…

13 min read

New
LLM Internals: Pretraining, Tokenization, SFT, and RLHF

Large Language Models (LLMs) are often described as black boxes, yet their behavior is the direct outcome of a determini…

15 min read

Browse by Topic

Courses and articles grouped by subject

DevOps & LinuxMicroservices & Distributed SystemsAI, LLM & Agentic SystemsDatabases & Data StorageSystem DesignAPIs & SecurityPerformance & CachingWeb DevelopmentEngineering Career Growth

Structured Curriculum

Each course is broken into bite-sized lessons you can complete in one sitting.

Hands-on Learning

Practice with real-world examples and build projects as you learn.

Learning Paths

Follow curated paths for backend, AI, full-stack, and system design interview prep.

Learning Paths

Curated sequences to guide your learning journey

Intermediate~25 hours
Backend Engineer Path

Build a strong backend foundation — databases, caching, inter-service communication, and system design.

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Intermediate~11 hours
AI Engineer Path

From RAG pipelines to agentic architectures — understand how AI fits into modern application stacks.

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Beginner~8 hours
Full-Stack Developer Path

Start with TypeScript and React, then Next.js and UI systems — the core modern web stack.

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Advanced~21 hours
System Design Interview Path

Prepare for system design interviews with fundamentals, patterns, and classic problem walkthroughs.

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Featured Courses

Popular courses to get you started

Performance
Intermediate
Caching
From fundamentals to production — caching strategies, eviction policies, invalidation, Redis, CDN caching, and multi-level architectures. Practical patterns and a guided final project you build in your own stack (no bundled starter repo).
~6.5 hours

14 lessons

View Course
Architecture
Intermediate
System Design Fundamentals
Learn how to design scalable, reliable, and maintainable systems — from single servers to distributed architectures used by millions of users.
~5 hours

12 lessons

View Course
Distributed Systems
Intermediate
Communication Between Services
Master how microservices talk to each other — synchronous REST and gRPC, async messaging, event-driven patterns, resilience, and distributed consistency.
~4.5 hours

10 lessons

View Course

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