The Visual Playground for Engineers

See it.
Try it.
Ship it.

Every concept comes in five formats. Read the article, tweak the simulator, watch the deep-dive, ship the code. Pick your depth, pick your moment, master the system.

Start with System Design → Browse Learning Paths

20

Concepts

5

Formats

4

Topics live

3

Learning paths

Five ways to learn each concept

Stack the modalities. Master the system.

Read the article. Tweak the simulator. Watch the deep-dive. Ship the code. Different formats for different moments — same concept, deeper every time.

📖

Article

Deep-dive read

🎨

Visualization

Interactive diagram

🧪

Simulator

Try it yourself

📺

Video

Long-form deep-dive

💻

Code

Build challenge

Featured

Start exploring

Payment System

How a tap on Pay travels through gateways, fraud checks, and settlement in under a second.

🎬 📖 🎨 🧪 📺 💻

Rate Limiter

Token bucket, leaky bucket, sliding window — the four classic algorithms behind every API quota.

🎬 📖 🎨 🧪 📺 💻

Uber Ride Request

Driver matching, geo-spatial sharding, and real-time location streams at city scale.

🎬 📖 🎨 🧪 📺 💻

SOLID Principles

Five rules that keep code flexible: Single Responsibility, Open/Closed, Liskov, Interface Segregation, Dependency Inversion.

🎬 📖 🎨 🧪 📺 💻

DRY · KISS · YAGNI

The three guardrails that stop over-engineering before it starts — Don't Repeat Yourself, Keep It Simple, You Aren't Gonna Need It.

🎬 📖 🎨 🧪 📺 💻

Singleton

One instance, shared by everyone. Useful for config and connection pools — dangerous everywhere else.

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The full universe

Eight topics. One playground.

System design first, then horizontally across every layer of the stack engineers actually work in.

Architecture patterns & trade-offs.

11 CONCEPTS Explore →

RAG, agents, inference, vector DBs.

6 CONCEPTS Explore →

20-lesson course: foundations + engineering practice.

20 CONCEPTS Explore →

Databases & Storage

B-trees, LSM, sharding, replication.

Distributed Systems

Consensus, gossip, leader election.

3 CONCEPTS Explore →

Networking, OS, data structures.

Auth, crypto, threat modeling.

Curated tracks for FAANG-style interviews.

Curated journeys

Learning paths

Hand-picked sequences that take you from zero to interview-ready or production-ready.

FAANG System Design

Top concepts asked at top-tier interviews

6 concepts · self-paced Start →

AI Systems Engineer

From RAG to inference to agents in production

6 concepts · self-paced Start →

Cosmos DB Engineer Ramp-up

Partitioning, RUs, change feed, Bw-Tree — live now

20 concepts · self-paced Start →

No signup. No paywall.

Pick your first concept.

Start with the animation, drop into the article, end on the simulator. Bookmark. Share. Repeat.

💳 Payment System 🔎 RAG Pipeline 📐 Vector DB