About SystemCraft
SystemCraft is a free, open interview prep platform for System Design (HLD), Machine Coding (LLD), DSA, and core CS concepts - built by engineers preparing at Amazon, Google, Meta, Flipkart, PhonePe, Uber, and startups.
We combine structured content with SensAI - an AI tutor that answers doubts, reviews code, gives hints, and conducts mock interviews - all in one place.
What makes this different
Most system design content online is either:
- Too shallow - “use a load balancer” without explaining why or when
- Too deep - 40-page production runbooks you’d never cover in 45 minutes
- AI-generated slop - rehashed bullet points with no real engineering judgment
SystemCraft sits at interview depth - deep enough to impress, concise enough to finish in one sitting. Every design is written as if you’re explaining it to a senior engineer interviewer.
What you’ll find here
System Design (HLD) - 39 designs
Each design follows a consistent, interview-ready format:
- Naive first cut - the simplest design and exactly why it breaks
- Prior art - real engineering blog posts from companies that solved this at scale
- Functional & non-functional requirements - prioritized ruthlessly (top 3 only)
- High-level design - components introduced incrementally with Mermaid diagrams
- Deep dives (Bad / Good / Great) - the hardest problems with progressive solutions
- Core flows - sequence diagrams showing runtime interactions
- Technology choices - what each tool does, why it’s chosen, and alternatives
Machine Coding (LLD) - 22 problems
Full runnable solutions in Java, Python, C++, and JavaScript:
- SOLID principles and design patterns (Strategy, Observer, State, Builder, etc.)
- Class diagrams and extensibility analysis
- Step-by-step thought process for machine coding rounds
DSA - 390 problems
- Integrated code editor with auto-complete, Run, Submit, and real-time judging
- Editorials with Intuition, Approach, Walkthrough, and Common Pitfalls
- Solutions in Java, Python, C++, and JavaScript
- Company tags (Amazon, Google, Flipkart, PhonePe, and more)
- Curated lists: Blind 75, Neetcode 150, Quick-Fire 50
Concepts and Fundamentals
53 topics covering system design building blocks:
- Databases, indexing, and replication strategies
- Caching patterns and invalidation
- Message queues and event-driven architecture
- Consistent hashing, rate limiting, and distributed consensus
- Load balancing, CDNs, and API design
Whiteboard
- Integrated drawing tool for system design diagrams
- Save and revisit your designs
- Practice drawing architectures the way you would in a real interview
Online IDE and Compiler
- Write and run code in Java, Python, C++, and JavaScript directly in the browser
- No setup required - just open and start coding
AI Features (SensAI)
- Ask SensAI - chat with an AI tutor on any page. It reads your code, diagram, or the content you’re studying and gives contextual answers.
- AI Hint - a one-sentence nudge when you’re stuck on a DSA problem, without spoiling the solution.
- AI Code Review - instant feedback on your submission: complexity, improvements, and what you did well.
- AI Mock Interviews - 30-minute timed sessions for both DSA and System Design, with voice interaction, real-time feedback, and scoring.
The philosophy
- Patterns over problem count. Recognizing “this is a fan-out problem” beats solving 500 random LeetCode questions.
- Show progression. Start simple, add complexity only when a requirement forces it.
- Tradeoffs over prescriptions. Every deep dive shows why the naive approach fails before presenting the fix.
- Real tech, real names. Redis, Kafka, Cassandra, Temporal - not generic “DB” or “queue.” But stay at design level, not implementation detail.
- AI as a tutor, not a crutch. SensAI gives hints and explanations, never full solutions. It’s like having a patient senior engineer on call.
Numbers
- 39 system design problems (Beginner to Advanced)
- 22 machine coding problems with full code
- 390 DSA problems with multi-language solutions
- 53 concept topics
- 5,000+ registered users
- 300,000+ monthly pageviews
Who built this
Built by engineers who went through the interview grind at Indian and international tech companies, got frustrated with the state of free system design content, and decided to build the resource that should have existed.
Shipped with obsessive attention to the details that interviewers actually care about.
Connect
- Website: systemcraft.in
- Email: systemcraft.in@gmail.com
SensAI