Are there two courses?

Yes. System Design has 770 lessons. AI Engineering has 214. You buy each one separately, with one payment each.

Does systemdesign.academy have an AI tutor?

Yes. Every lesson in both courses has an AI tutor beside it. While you read a lesson, the tutor reads the same lesson and answers from it. It can explain a part in simple English, draw it as a whiteboard sketch, a 3D figure, a cloud diagram with AWS, Azure or GCP icons, a sequence diagram, an explainer figure or a cheat-sheet poster, quiz you, run a mock interview, or compare two things. Under most lesson slides there are buttons that ask it to explain that part, draw it, or quiz you on it. In a quiz, the site's own code checks your answer against the answer key the tutor wrote with the question. It also has its own page at /tutor. Without an account you can ask 2 questions a day to try it. A free account gets 5 questions a day. Anyone who owns either course can ask as many questions as they like.

What can the AI tutor do?

It explains any system design or AI engineering idea in simple English, and it draws: a whiteboard sketch, a 3D figure, a cloud diagram with AWS, Azure or GCP icons, a sequence diagram, an explainer figure or a cheat-sheet poster. It can also quiz you, run a mock interview, or compare two things in a table. When a lesson covers your question, it links to that lesson, and every lesson link in an answer is checked against the real lessons before you see it.

Does the AI tutor know the lesson I am reading?

Yes, when you can read the lesson. If the lesson is free or you own its course, the tutor gets the lesson's text and answers from it first. On a lesson you have not unlocked, it only knows the lesson's title, so it helps in general terms and does not hand the lesson over.

What does the AI Engineering course cover?

It has 214 lessons in 17 chapters: LLM Evaluation and Error Analysis (36 lessons); LLM and GenAI Ops (15 lessons); Agents in Production (14 lessons); Data Engineering for ML (14 lessons); Features and Feature Stores (12 lessons); How Models Generate (12 lessons); Prompting as Engineering (12 lessons); Retrieval and RAG in Production (12 lessons); Serving and Inference Basics (12 lessons); Tokens and Embeddings (12 lessons); AI Security and Agent Safety (11 lessons); Fine-Tuning: The Narrow Decision (11 lessons); Core Concepts (10 lessons); Packaging, Registry and Versioning (10 lessons); The ML & AI Lifecycle (10 lessons); Why Production Breaks (7 lessons); Monitoring, Drift and Evaluation Basics (4 lessons). It is about building and running AI systems in production.

Is there a course on RAG, AI agents or LLMOps?

Yes. The AI Engineering course has a chapter on each: Retrieval and RAG in Production (12 lessons), Agents in Production (14 lessons), LLM and GenAI Ops (15 lessons). Evals have their own chapter too: LLM Evaluation and Error Analysis (36 lessons). The course costs ₹1,333 in India or $35 everywhere else, once, with lifetime access.

Is the AI Engineering course hands-on?

Yes. Every lesson has Python you can run in your browser, and a quiz. 122 lessons are built on a lab that was really run, and show the terminal recording of that run. Several chapters measure things with small models running on a laptop.

Who runs systemdesign.academy?

Roni Das. He writes both courses and publishes on the YouTube channel Total Technology Zonne. The site has been online since April 2026, and its only address is www.systemdesign.academy.

How much do they cost?

System Design: ₹1,111 in India, $25 everywhere else. AI Engineering: ₹1,333 in India, $35 everywhere else. Each course is one payment, and it is yours for life.

Can I try before I buy?

Yes. 18 System Design lessons and 10 AI Engineering lessons are free. You do not need to sign up to read them.

Is this a video course?

No. Lessons are written, with diagrams that build step by step, quizzes, and in many lessons live code you can run in your browser. You learn by reading and doing.

What do I need to know before I start?

Nothing. The first lessons start from zero, with questions like "what is latency?". The later ones reach distributed consensus and running AI systems in production.

Does it help with system design interviews?

Yes. Besides the lessons, there are 106 system design pages, from Discord to Swiggy, written the way you would answer in an interview. They are free to read.

How long do I keep access?

For life. That includes every lesson added later to the course you bought.

This is a digital course. All sales are final and there are no refunds. Please read the free lessons first (18 in System Design, 10 in AI Engineering) to decide before you pay.

By Roni Das · two courses, System Design and AI Engineering

System Design Masterclass See how real systems are built. Then build your own.

984 lessons that draw every idea step by step, across the System Design Course and the AI Engineering course, and 106 real systems taken apart, from Discord to Swiggy.

two courses · pay once, yours for life

course 1

$25

System Design Masterclass

770 lessons · 106 real systems taken apart

Get System Design or read 18 free lessons

course 2

$35

AI Engineering

214 lessons · RAG, evals, agents · labs on real models

Get AI Engineering or see the course first

UPI, card or netbanking in India · card or PayPal everywhere else

See the packs

Try 3 interactive concepts free: learn one idea in about 10 minutes →

984lessons

3,049live diagrams

106systems taken apart

1AI tutor that draws

Stuck? Ask the tutor. It answers with a real diagram in about 30 seconds.

Detail A · live whiteboard

Userson phones

CDNimages, JS

Load balancer

Metrics

Kubernetes pods

APIcopy 1

APIcopy 2

APIcopy 3

Cache

Queue

Workers

Primary

Replica

async copy

replica may lag

hot data, from memory

Your turn: design it

add copies

to scale out

↑ redraws itself: web app · Kafka · hashing · RAG. Pick one.

Detail B · from an explainer video

A still from an explainer video: 200 chats served by one GPU chip, drawn as a grid of phone screens.

↑ a still from one of our explainer videos. More are being added inside the courses.

How Discord stores trillions of messages

A real system, step by step

Discord app

You send a message in a busy channel.

Discord API

One large service takes the request.

Data service, in Rust

Many people ask for the same data at once. It asks the database only once.

3 asks in,
1 ask out

same data,
same service, every time

ScyllaDB

Stores the messages.

72 machines now. All the dots = the 177 Cassandra needed.

Loading older messages · the slowest 1 in 100

Where the messages lived

MongoDBat the startCassandra177 machinesScyllaDB72 machines

STEP 6 OF 6The slowest 1 in 100 reads of older messages went from 40 to 125 milliseconds down to 15.

Source: Discord engineering blog, “How Discord Stores Trillions of Messages”

Title · DWG SDA-001Field notes for engineers who ship

Drawn byRoni Das

Checkedmeasured in labs

Sheet1 of 984

Rev2026.09 · systemdesign.academy

New · for students

12th pass or in B.Tech? Start your software engineering journey the right way

Free Starter Track12 free steps in a beginner's order: lessons, interactive concepts, a roadmap and two PDFs.Start free →Live: Campus to Career Launchpad12 weeks, Mon, Wed, Fri evenings, from Mon 16 Nov. Code, DSA, SQL, projects and placement prep. For students in India: ₹25,000.See the 12 weeks →

Open the student page

NEWSystem Design Hands-On

Included in the System Design course: real systems, built live

Postgres Sharding: Complete Hands-On (PgBouncer + Citus). 2 h 36 min and 20 chapters: one PostgreSQL loaded until it breaks, then four shards behind a router you write, PgBouncer and Citus, with the 139-page slide deck. The first 15 minutes are free to watch.

Watch the free 15 minutes See System Design Hands-On

New: live weekend classes, batch starts Saturday 7 Nov

All live classes

Spec sheet · the short version

What is systemdesign.academy?

systemdesign.academy is an online school run by Roni Das, with two self-paced courses and an AI tutor built into every lesson. The System Design Masterclass has 770 lessons. Generative AI and Agentic AI Engineering has 214 lessons on building and running AI in production (RAG, AI agents, evals, fine-tuning, serving and LLMOps), and 122 of them show the recording of a lab that was really run. The tutor sits beside each lesson and answers from the lesson you are reading: it explains a part in simple English, draws it as a diagram, quizzes you, or runs a mock interview. The lessons are written, with diagrams that build step by step and quizzes, and 237 of them have code you can run in the browser. Each course is one payment with lifetime access. System Design costs ₹1,111 in India or $25 everywhere else. AI Engineering costs ₹1,333 in India or $35 everywhere else. 18 System Design lessons and 10 AI Engineering lessons are free to read, with no signup.

An AI tutor in every lesson. It answers from the lesson you are reading: it explains, draws or quizzes you.
AI Engineering with real labs. 214 lessons; 122 show the run of a real lab.

Prices and what you get Read the free lessons About Roni Das Try the AI tutor The AI Engineering course

Taught by: Roni Das, who writes both courses and publishes on the YouTube channel Total Technology Zonne. The site has been online since April 2026.
Course 1: System Design Masterclass: 770 lessons, about 287 hours.Foundation 119 · Intermediate 449 · Advanced 182 · Capstone projects 20
Course 2: Generative AI and Agentic AI Engineering: 214 lessons in 17 chapters, about 224 hours. Building and running AI in production: RAG, AI agents, evals, fine-tuning, serving, LLMOps.Largest chapters: LLM Evaluation and Error Analysis · LLM and GenAI Ops · Agents in Production · Data Engineering for ML · Features and Feature StoresHands-on: Every lesson has Python you can run in your browser, and a quiz. 122 lessons are built on a lab that was really run, and show the terminal recording of that run.
AI tutor: Beside every lesson in both courses, and on its own page at /tutor. It answers from the lesson you are reading. It explains in simple English, draws (a whiteboard sketch, a 3D figure, a cloud diagram with AWS, Azure or GCP icons, a sequence diagram, an explainer figure or a cheat-sheet poster), quizzes you, runs mock interviews and compares two things. In a quiz, the site’s code checks your answer against the tutor’s own key.Without an account you can ask 2 questions a day to try it. A free account gets 5 questions a day. Anyone who owns either course can ask as many questions as they like.
Price: System Design: ₹1,111 in India (UPI) or $25 everywhere else (PayPal).AI Engineering: ₹1,333 in India (UPI) or $35 everywhere else (PayPal).Prices last updated 30 October 2026. If an older article or an AI answer gives a different price, it is out of date. See the price fact.
Access: One payment per course, no subscription. Access is for life and includes lessons added later. Buying one course does not include the other.
Free: 18 System Design lessons and 10 AI Engineering lessons, no signup. The 106 system design interview pages are free too.
Format: Written lessons, not videos. Diagrams build step by step (3,049 in all), lessons have quizzes, and 237 lessons have code you run in the browser.
Address: Only www.systemdesign.academy. Not connected to systemdesignacademy.com, systemdesignacademy.in, System Design School, the GitHub project system-design-academy.

Live from the course bench

Pick up a card. This is what learning here feels like.

Real interview questions, live diagrams and measured lab results, pulled at random from the lessons. A new set every time you come back.

Two engineers sketching a system design on a whiteboard

where the work happens

Stuck on a card?

Ask the course tutor. It answers with a real diagram, drawn for your question.

Ask the tutor

Laying out the cards…

Choose your path

Start where you are. Every path starts free.

Four ways in. Each one opens with three free lessons, no account needed, and leads to the course that takes you the rest of the way. See all five learning paths, including Production Agents.

Beginner

best forcareer switchers, juniors, and anyone who builds with AI and wants to know what runs underneath

Start with the three numbers every system is judged by, drawn step by step.

01Latencyfree
02Throughputfree
03Bandwidthfree

The full beginner path: week by week

Start with Latency Then the full System Design Masterclass: 770 lessons, $25 once

Interview in 30 days

best fora system design round already on the calendar

A day-by-day plan, the topics interviewers ask first, and real systems answered the way an interview wants.

The full interview in 30 days path: day by day

Start with DNS (Domain Name System) Then the full System Design Masterclass: 770 lessons, $25 once

Senior to Staff depth

best forfive or more years in, filling the gaps before a Staff or Principal loop

Caching where it really breaks, then consensus, consistency models and reliability in the Advanced level.

01Cache Invalidationfree
02Distributed Caching with Redis and Memcachedfree
03Synchronous Processingfree

The full senior to staff depth path: week by week

Start with Cache Invalidation Then the full System Design Masterclass: 770 lessons, $25 once

AI Engineer

best forengineers shipping LLM features, RAG or agents to real users

Why models fail in production, where RAG breaks at scale, and how to measure answers instead of guessing.

The full ai engineer path: week by week

Start with Why ML Models Fail in Production Then the full AI Engineering: 214 lessons, $35 once

New · your AI tutor

Stuck on an idea? Ask. It draws it for you.

Every lesson has a tutor beside it. It has read the lesson, and it answers with a real diagram, drawn for your question, in about half a minute.

Explains any idea in plain English, from the lesson you have open.
Draws whiteboard sketches, 3D figures, AWS, Azure and GCP diagrams, sequence diagrams and cheat-sheet posters.
Quizzes you and runs mock system design interviews with feedback.
Points you to the exact lesson that teaches it.

Try the AI tutorFree accounts get 2 questions. Course owners get 10 a day.

A hand-drawn sketch the tutor drew: browser, DNS, web server, app code and database in a row, each hop labelled with its time, with red notes that a cached DNS lookup is skipped and a missing index costs 500 ms or more. — A real answer from the tutor, asked from the Latency lesson. It took about 30 seconds.

Drawn by the tutor

One question each. Real diagrams back.

3D figure. Asked: “Kafka producers, brokers and a consumer group”
AWS diagram. Asked: “A web app on AWS with a load balancer, containers and PostgreSQL”
Sequence diagram. Asked: “How OAuth login works”
Explainer figure. Asked: “How a CDN serves an image”

Ask your own question →

Try it live · no sign-up

Ask the tutor. See what it does.

Press a question. It explains, draws or quizzes you, the same way it does beside every lesson.

Checking the tutor…

Each button sends exactly its words to the real tutor. Its answer is saved, so the next person sees it at once, and it is asked again after 3 days.

Pick a question. The tutor’s real answer appears here: plain words, a drawing when one helps, and the lesson that teaches it.

Then ask your own. A free account gets 5 questions a day; either course gets unlimited questions, beside every lesson.

Try it on how Uber matches a rider to a driver, how Stripe never charges twice or how WhatsApp delivers a message, then ask the tutor how you would build it.

One payment, lifetime access. Pay with PayPal.

106 real systems, taken apart

Pick a system. See how it really works.

Each one is a full page: what it must do, the numbers it faces, the parts it is built from, and the choices you would defend in an interview. Free to read.

See all 106 systems → or the system design interview questions with short answers.

Measured, not guessed

Other courses tell you. Ours run the test.

Every number below comes from an experiment we ran and published in a lesson of the AI Engineering course.

Search got better. Answers got worse.
Recall went from 45% to 90%. Right answers fell from 10 to 6, out of 20 questions.
Lesson 98 →
Almost half the score came before search.
With no documents, the answer already scored 6.7%. With them, 15.1%. So 44% of the score was there before retrieval ran.
Lesson 99 →
Move one document, and 4 right becomes 14.
The same 10 documents every time. The right one in the middle: 4 of 14 correct. At the end: 14 of 14.
Lesson 100 →
Three points better? Maybe not.
With 100 test questions, one 80% score could really be anywhere from 72% to 88%.
Lesson 88 →

Two courses, one payment each

From your first API call to AI in production.

System Design

770lessons

Foundation119
Intermediate449
Advanced182
Capstone projects20

Try a lesson: Data partitioning across nodes · Read-through caching · Distributed locks · Snapshot isolation and write skew

18 lessons are free to read, no sign-up needed.

Start with the free lessons

AI Engineering

214lessons

LLM Evaluation and Error Analysis36
LLM and GenAI Ops15
Agents in Production14
Data Engineering for ML14
Features and Feature Stores12
How Models Generate12
Prompting as Engineering12
Retrieval and RAG in Production12
Serving and Inference Basics12
Tokens and Embeddings12
AI Security and Agent Safety11
Fine-Tuning: The Narrow Decision11
Core Concepts10
Packaging, Registry and Versioning10
The ML & AI Lifecycle10
Why Production Breaks7
Monitoring, Drift and Evaluation Basics4

Try a lesson: What a token is · The context window, measured · Tail latency: the slowest 1% · Building a golden dataset

10 lessons are free to read, no sign-up needed.

See the AI Engineering course

Try it right here

Change the numbers. Press Run.

This is Discord’s idea from the top of the page, in a few lines of Python. It runs in your browser. No sign-up.

237 lessons have a box like this one.

# 1,000 people open busy channels at the same moment.
requests = ["general"] * 700 + ["random"] * 250 + ["memes"] * 50

# Without a data service, every request goes to the database.
without = len(requests)

# With one, identical requests wait for one shared answer.
with_service = len(set(requests))

print("Database reads without it:", without)
print("Database reads with it:   ", with_service)
print(f"That is {without // with_service} times fewer.")

The engineer behind it

Roni Das

Lessons and tutorials at systemdesign.academy

Roni builds large scale systems, then breaks them down so you can see how they work. He made the System Design Masterclass and the AI Engineering course, and runs the YouTube channel Total Technology Zonne.

Two full-length handbooks on freeCodeCamp: building a knowledge graph, and building a GraphRAG system, with Python and Neo4j. Read them
Watch Total Technology Zonne on YouTube

Price

Pay once. Keep it forever.

The two courses are sold separately. Buy one, or both.

System Design

$25once

770 lessons, and every lesson added later
18 of them free to read first, no sign-up
One payment. No subscription. Yours for life.

Buy for $25

AI Engineering

$35once

214 lessons, and every lesson added later
10 of them free to read first, no sign-up
One payment. No subscription. Yours for life.

Buy for $35

What you get

System Design Masterclass

770 lessons, from latency to consensus
106 real systems taken apart, step by step
Includes System Design Hands-On builds: Postgres Sharding, 2 h 36 min built live, with slides
Diagrams that build step by step, quizzes and runnable code
AI tutor beside every lesson, unlimited questions
Lifetime access, including every lesson added later

Read the free 18 lessons first

AI Engineering

214 lessons in 17 chapters
Python you run in the browser, in every lesson
122 lessons built on a lab that really ran, with its recording
AI tutor beside every lesson, unlimited questions
Lifetime access, including every lesson added later

Read the free 10 lessons first

Not included: Live classes or one-to-one mentoring. Each course can be bought on its own, or both together in one payment.

How you pay: India: UPI, card or netbanking through Razorpay (₹1,111 / ₹1,333). Everywhere else: card or PayPal ($25 / $35).
After you pay: As soon as your payment is confirmed, your access unlocks and you get an email.
Help: inboxtoroni@gmail.com
Refunds: This is a digital course. All sales are final and there are no refunds. Terms

Course last updated 25 Oct 2026

New: free concepts

Free concepts: learn one idea by predicting it

How a Database Index Finds a RowA million rows, one id. Without an index, how many rows does the database read?Sharding With Consistent HashingAdd a fifth server to four. Guess how many keys hash mod N makes you move.Kafka Partitions and Consumer GroupsSix partitions, eight consumers in one group. How many sit idle?

All concepts

Just explained

This week in AI, run and explained

When a new model or tool ships, we try it ourselves and write down what it means for the systems you build.

All explainers

31 Oct 2026 · 17 min read

Kimi K3.1 Pro, explained: what Moonshot shipped, what it costs, and why the thinking you send back adds upKimi K3.1 Pro is the newest large AI model from Moonshot AI, a company in China. It went live on 23 October 2026 in Moonshot's API and its coding tool Kimi Code, and Moonshot says the weights (the model files anyone can download) will be public by 4 November. It is the same model as Kimi K3, with 2.8 trillion parameters (the numbers a model learns in training), trained further, and it costs a third less than K3 on Moonshot's API. I read Moonshot's own pages, ran its prompt code and tokenizer on my Mac, and worked out what an agent task costs when, as Moonshot requires, you send the model's thinking back on every step.Kimi K3.1 ProMoonshot AIKimi K3open-weight modelsread the explainer 30 Oct 2026 · 11 min read

CVE-2026-111497 (Node2Shell), explained: the Brotli bug in Node.js, .NET and Envoy, and how to checkCompressed data is unpacked all the time without anyone asking: a web reply, an upload, a font. A bug in Google's Brotli decoder lets one crafted compressed stream write past the end of a buffer, which can crash the program, leak its memory or run an attacker's code. It is being exploited, it is on CISA's must-patch list with a 10 November deadline, and Node.js, Bun, .NET, Envoy, Istio and Python have shipped fixes.CVE-2026-111497BrotliNode2ShellBroccoli2Shellread the explainer 29 Oct 2026 · 14 min read

Two cards. gemini-4-argon: Fairwind partners from 30 September, developers from 13 October, on our API key's model list today. gemini-4-carbon, drawn dashed: cyber defenders from 28 October, and the guessed id returns HTTP 404. Underneath: Argon took 13 days to reach developers; Carbon has no date yet.

Gemini 4 Carbon, explained: Google's security model, who gets it first, and how to test a code fixGoogle announced Gemini 4 Carbon on 28 October 2026 as its strongest model, built for finding and fixing security holes in code. Only a group of cyber defenders can use it for now, so I checked our API key, then built the small test harness that decides whether any model's security fix actually works.Gemini 4 CarbonGoogleGemini APIsecure codingread the explainer

Free to read

New guides

Questions

Questions before you buy

not sure yet? read the free lessons first

Start with the free lessons. Pay only if they change how you think.

Read 18 free System Design lessons See the AI Engineering course

System Design Masterclass See how real systems are built. Then build your own.

12th pass or in B.Tech? Start your software engineering journey the right way

Real interview questions, answered in full.

Included in the System Design course: real systems, built live

What is systemdesign.academy?

Pick up a card. This is what learning here feels like.

Start where you are. Every path starts free.

Stuck on an idea? Ask. It draws it for you.

One question each. Real diagrams back.

Ask the tutor. See what it does.

Pick a system. See how it really works.

Other courses tell you. Ours run the test.

Search got better. Answers got worse.

Almost half the score came before search.

Move one document, and 4 right becomes 14.

Three points better? Maybe not.

From your first API call to AI in production.

Change the numbers. Press Run.

Roni Das

Pay once. Keep it forever.

Free concepts: learn one idea by predicting it

This week in AI, run and explained

New guides

Questions before you buy

Are there two courses?

Does systemdesign.academy have an AI tutor?

What can the AI tutor do?

Does the AI tutor know the lesson I am reading?

What does the AI Engineering course cover?

Is there a course on RAG, AI agents or LLMOps?

Is the AI Engineering course hands-on?

Who runs systemdesign.academy?

How much do they cost?

Can I try before I buy?

Is this a video course?

What do I need to know before I start?

Does it help with system design interviews?

How long do I keep access?

Can I get a refund?

Start with the free lessons. Pay only if they change how you think.

What learners say