Why did I join the course? (ordered randomly) - Simple -

1. Depth

2. Knowing what I don't know about ("You don't know what you don't know")

3. Knowing you, philosophies, the network, everything.

This cohort gives you all.

The best is the idea of evolution with each design. Choose x (all good? yes. - Nope), "what's wrong with this ", tradeoffs?, how to make it better to reach y, ...

I have incorporated this in my notes, in my thinking pattern, everywhere. This is how we should think, actually (makes thinking easier too). You have structured the course so well! All the dabbas are easy to understand - now one can reason about things.

By the 7th week itself, the main designs are just a reference of week 3, week 4, and copy and paste. It's drilled down! That's actually the best part now that I reflect, pre-requisites, and building on older ideas to teach new ones, thereby ensuring people have to recall stuff, spaced repetition.

Apart from this, the times when you repeat things just to drill things into our heads - make it hard to forget XD. Actually, this is one aspect that made me feel that you're a good good teacher. Of course, 50k is no joke, but frankly, this is really 1000x better than any college course or any other teaching material.

The fact that you improve your critical thinking, the discipline this has instilled, every weekend, 7 am at the table, studying, reviewing notes, for learning! (saying no to house parties, because well, sessions are expensive XD)

I'm pretty sure now I'll think around the code aspect, train myself on thinking implementation (even with AI around) because that (as you have shown) brings out the actual issues that require an engineer's mind. Lastly, every morning 15 mins early, to catch up with you, just chit-chatting is so much fun.. Always get to learn new things from you, be it technical, industry or life XD

Generally, after this, I keep on rambling the whole day to my wife, what I discussed with you, what you do, how you are interviewing etc. I'll miss that after the course, OF COURSE.

You are the Rancho of software engineering :P

But in all seriousness, thanks for everything, Arpit. In 8 weeks, you have given everything that is required for any engineer taking this course to succeed, that's all we can ask for.

This course covers enough depth that if you stay attentive throughout, it equips you with everything required to succeed — whether you're a SDE-2 or Staff-level Engineer.

What sets Arpit apart is how he trains you to think. System Design has always been about tradeoffs, understanding the product, and requirements. He forces you to approach problems from all these angles — Business > Product > Engineering.

The idea of evolution in every design is what I found most valuable. You start with the simplest approach, identify its tradeoffs, iterate toward a better solution, and keep going. This way of reasoning is now part of how I think about systems, and it applies well beyond interviews.

The course structure deserves special mention. Concepts build on each other methodically. By week 7, the advanced designs are essentially compositions of building blocks from earlier weeks. Pre-requisites are covered first, then layered upon, which naturally forces recall and reinforces retention.

It also builds critical thinking and discipline. Every weekend, dedicated hours, reviewing notes, going deeper, because the material demands and rewards that level of engagement.

Having explored various learning resources over the years: university courses, books, online content, I can say with confidence that this is significantly more effective than anything else I've come across.

You don't just learn system design. You learn how to think about it.

I took a deliberate career break in 2025 to focus on my personal and professional growth. Investing in this course was the best investment of my time to upskill myself and it won't be an overstatement if I went on to say that this was one of the best investments of my life.

Apart from a deep passion for engineering Arpit has a natural knack for teaching and explaining complex problems by simplifying them which makes this course extremely rewarding. When I first joined this course and I saw Arpit's passionately talk about Engineering problems, I remember thinking to myself that I was in the wrong field, that it was meant for people as curious and as smart as Arpit. I felt I was already too late in the race and questioned if I should even be running this race in a world of AI where everything is moving so fast.

But genuine passion and commitment towards something has a way of rubbing on to others. Towards the end of the course I felt more confident in myself and I was eager to go apply my renewed understanding of systems.

Kudos to Arpit for curating such a rich course which touches on so many design patterns. Also it indeed is a no-fluff course - it is not merely focused on getting you to crack interviews but instead focused of building your intuition and over time you learn to recognise patterns.

There is so much to extract from this course with the pre and post reads and the hands-on exercises that Arpit recommends. The brainstorming sessions keep the class interactive and help you identify your biases and fallacies. You also learn a lot from the peers in the cohort who share their own first-hand experiences.

I am sure I will keep revisiting these class recordings for a long long time and absorb new things every single time. I am so glad I decided to enroll in this course and I highly recommend it to anyone wanting to dig deeper and approach System design from the first principles.

I highly recommend this course to any software engineer, whether you're preparing for interviews or simply looking to level up. Despite 12 years in the industry, I've never had this much clarity on the moving parts of complex software systems.

In the past, I've spent countless hours diving into blogs and articles only to be left with more questions. Within the first two weeks of this masterclass, I realized I could trust Arpit to break down even the most complex concepts with guaranteed clarity. I especially valued his teaching style—he doesn't just ""cover a topic""; he pushes the cohort to think critically through every problem statement. From database internals to WebSockets and Bloom filters, I've moved beyond surface-level theory to actually understanding how to choose the right tools for a specific business case.

Teaching is a hard skill and Arpit does it with ease. I am leaving the course with a lot of learnings and confidence.

PS: Of course I have used Gemini to rephrase the testimonial, because the gratitude in my own words went beyond a page :)

Thanks Arpit for teaching. Keep going!!!!

The sheer depths to which each conversation went. I now don't accept components or systems at face-value (let's stick Kafka here, let's use Redis there) - instead, and that has helped me refine my thinking.

I believe Arpit starts where other people stop, and that's the differentiated value-add I got from this cohort.

Arpit clearly knows this subject inside and out, and his passion for it comes through in every lesson. What sets him apart is that he doesn't just cover the technical side - he thinks in multiple dimensions:

• Business constraints

• Infrastructure cost

• Operational complexity

• Trade-offs

It's all in there.

He reminded me that keeping things simple is harder than it sounds, and that we as engineers tend to over-reach. Sometimes writing to disk and running a cron job is the right call. Sometimes the business solution beats the engineering one.

The word dictionary exercise stuck with me. Building an append-only log and constructing indexes over it made things like write-ahead logging click in a way that reading about it never did.

No perfect solution. Only trade-offs. That's the mindset I'm taking away from this course.

Arpit's energy and passion are contagious. I really like that the course focuses on building better systems instead of just chasing trendy buzzwords. He goes deep into implementation, and a big part of each session feels like collaborative brainstorming.

I especially appreciate how conversations naturally include the business and product perspective, because in the real world, those factors often make the final difference.

I'm definitely going to miss these discussions.

I joined Arpit's course at a time when my work had become chasing deadlines, closing tickets, and just "getting things done" for sake of meeting deadlines. I had almost forgotten the excitement I used to feel when I first wrote a small HTML file and saw it magically open in the browser. This course has helped me bring that spark back.

What I really liked is that it's not a typical monologue-style course. It feels more like an open design discussion. Everyone gets a chance to think, speak. Arpit constantly pushes you to go deeper and build strong mental models, so you don't just solve the 30 problems discussed, you learn how to solve thousands more. You start seeing patterns everywhere.

The biggest takeaway for me was simple: doing is everything. The more you build yourself, the better you get. And this course encourages you to build.

Honestly, this has been one of the best educational investments I've ever made.

I would like to thank my colleague Ashish for suggesting such an exceptional cohort. Thank you is such a small word for what this cohort has unblocked for me. I am now able to think in the right direction and now I know what is going behind. Now I know what not to draw on the canvas just for the sake of filling the space. What I loved most is the assignments provided by Arpit and a motivation that I can do that.

Believe me, I can't express my feelings every time when I created the system that was given as an assignment. It always felt like I burst the hoax about complex systems like LB, Kafka, Bitcask etc that we see specially for the engineers who don't get chance to work with the high scale system.

I would never know that LSM is such a powerful storage element which powers loads of complex systems which magically handles the scaling.

Thank you so much Arpit for making me believe that I can handle any counter question about complex systems whatsoever.

You short of developed a blueprint in my mind to tackle system design. Now my mind doesn't start by drawing complex boxes rather start with bare minimum solutions available and then incrementally handle complexities with the available buffet of knowledge around complex solutions available.

You developed a taste in me to read research papers, and now I have started reading papers for all the available systems and try to understand the functionalities by querying LLMs until I am fully satisfied with the results.

Thank for developing that zeal, interest and curiosity to understand all the systems. I will also subscribe for the codecrafter course to further gain the confidence.

I will really miss the sessions :(

Arpit has a rare gift — he makes technical depth feel accessible without ever dumbing it down. His session was one of those experiences where you walk in knowing things, realize how deeply rooted they are and walk out truly understanding them.

The framework he shared was clear, practical, and immediately actionable. But what really stayed with me was how he explained every single question in the end which felt natural and engaging.

I came in with zero knowledge in system design, and left with real confidence in dealing with practical system design scenarios. If you ever get the chance to learn from Arpit, take it — you won't regret it.

This is not another System Design course which you take, Arpit pours his real world experience in teaching how to approach a problem and how to approach any system design.

He doesn't just teach how its done, but makes the students think hard of the 'WHY', keeping in mind all pros and cons.

This course is highly recommended for anyone who wants to improve upon the process of coming up with a design/architecture.

A huge thank you to Arpit for these incredible sessions. I've rarely encountered a learning environment where topics are explored with such immense depth.

Arpit's breadth of knowledge is remarkable; he has an answer for every question, but more importantly, his focus on probing and brainstorming forces you to think broader. That mental shift stays with you long after the session ends.

Between the curated pre-reads and deep-dive post-reads, he truly masters the art of building curiosity.

I highly recommend his YouTube, blogs, and courses to anyone looking to level up.

I loved the sessions for the past two months. Did learn a lot about both tech and how to think from the perspective of a company and business and Product. Definitely recommending it to anyone who wants to build understanding of systems and make informed tradeoffs for systems and think of implementations on each turn. Plus the three corners Business, Tech and Product.

And the genuine curiosity, enthusiasm and his want to teach you will definitely light a spark that you had back from College days.

10/10 recommended

One of the best things I've learnt from Arpit in this course is that devil is always in the details. Quite often most youtube videos/ courses I've seen mention a high level design for a system but once you start digging into the details it often does not make sense.

I really liked the way Arpit directed each session in the course, forcing everyone to actually think how a component would work rather than listing terms.

I joined this course mostly out of curiosity and a little “am I missing something everyone else knows?” feeling. I wasn’t expecting a mindset shift, but that’s honestly what I got.

What stood out to me is how simple system design felt when explained the right way. Instead of getting lost in fancy terms or patterns, the course focused on intuition: understanding the problem, breaking it down, evaluating trade-offs, and choosing what makes sense. It made me realise that solving hard problems isn’t about complexity, the real skill is simplifying things in a way that still works.

I’ve been following Arpit since my college days, and even back then I loved how he explained things so clearly and to the point. That same clarity carried through in this course, even the seemingly complicated topics felt simple and understandable.

The examples, discussions, and reasoning frameworks made the learning stick instead of just floating around as theory. I could actually connect things to how systems are built in the real world, and that gave me a lot more confidence in how I think and approach problems now.

Also really appreciated how patient and open Arpit was throughout the sessions. You could ask anything, basic, random, detailed, and he’d break it down with clarity and honesty, not buzzwords.

And yes, the classic line: “If you have a hard problem, don’t solve it.” Somehow makes me feel better about not overcomplicating things -- pure genius. xD

I have been following Arpit on Twitter for about 2 years now and always loved that each week led to some form of learning whether it was the papers he shared or the videos he produced. It made me interested in how to think than learning what to think.

I used to see the feedback on his course but always felt that I was not ready for it. This year is when I decided to give it a shot and my only regret would is that I didn't take it up earlier.

The systems that we learned to breakdown and the manner in which we did further reinforced the principle of "how to think" rather than what component would fit in.

We covered many topics/components which I have used many times but never stopped to think what it was meant to solve or to replace. The best learning that I take home from this course is that every time I come across a site, a product or a claim of high performance, my immediate thought would be to think of what they intended to solve and how to break it down into simple components.

As we covered:

• LSM trees

• Databases

• KV stores

• Load balancing

• Distributed schedulers

it becomes clear how nuanced the thought process is and how by simple layering of the requirements we can solve complex problems.

I would highly recommend this course to all people who are looking to learn or take the next step in their career.

Now onto all those exercises to complete :)

This cohort based course is a blessing in disguise (Disguise being the learning systems to the depth). The very idea of thinking, learning and doing what matters; this masterclass is a prime example of it coming to life. In this cohort we just were helped to understand not just what is more important but also why! This course can definitely help people understand the meeting point of business and innovation. And once you reach there; technology is one the sassiest tools you can leverage, impacting millions.

In every single decision of working with systems (from a bird-eyes view down to implementational challenges), we always had trade-offs discussed, new ideas appreciated, and every question that came onto the participants head spoken out answered (or given the right direction). We were taught to understand our own patterns of getting stuck, and also how to come out of it by making us understand where do these patterns are coming from. We understood the common patterns that are followed across the technology stack, and how to stitch them together. The very core of practicality where we re-used ideas, built on top of it with different nuances, understood the importance of SIMPLICITY.

I took the course to learn more, I had no aim for learning to interview only. And it worked wonders. I was able to grab more challenging initiatives at my work even when I was still attending the course.

Some key takeaways as an engineer that I found unique to this cohort:

• Framework of opposites, helps you identify trade-offs better. Also, might even help you solve problems with innovation trying to get into the middle grounds!

• You can understand complex systems by building simple prototypes.

• (Not discussed directly but personal takeaway) Low level designs are often derived from High level simplified choices for seemingly complex systems.

• When working with large scale, to save costs and making systems simpler, it's Space vs Time vs Correctness.

The course is very smartly curated where a lot of breadth in technology is covered linking one to other, helping you understand systems at scale is nothing but having Plan B for your Plans B. The course is enough to inculcate the importance of the three basic questions: Why, What, and How. I grew up with focusing only on ""Why"", and sessions with Arpit just helped me understand What and How are equally important, wherein you start to grasp in which situation either of the question has how much weightage!

For someone who thrives on engineering wonders this course a nitro-boost and for folks who are yet to identify their interests in engineering, this course is a reality identification on how beautiful engineering is.

I've always had a habit of reading an author's profile whenever I come across their blog. One day, while reading about the Morris Approximate Counter, I found your blog and discovered your courses. I came across the Redis Internals course and became very curious about it—especially the idea of writing a Redis-like database in Go, so I enrolled.

I genuinely enjoyed it and felt grateful to learn about Redis internals. Through this course, I also learned:

• Go

• OS kernel Epoll

• How a single thread can accept connections

Later, I came across the System Design Masterclass and enrolled in that as well. Once again, I felt truly blessed to understand how real systems work. For me, it's really an ocean of content to absorb. Every session was filled with so much information that I often fell behind, and I'm still trying to read more and make things clearer, especially while managing a busy office work schedule.

I really want to thank you for creating these courses.

Thank you so much, Arpit!!

:-)

"Master of Prototyping: The Catalyst for Deep System Understanding"

Arpit is a true master of prototyping, explaining system design from the business objective through the architectural plan right down to the code-level implementation.

I want to personally thank Arpit for this masterclass. He literally worked as a catalyst for me, enabling me to build systems quickly and understand the deep nuances of implementation, rather than just focusing on building high-level boxes. This shift in mindset and technical approach has been game-changing.

In the last eight weeks alone, I have successfully built and prototyped many systems, achieving end-to-end comprehension, writing robust code, and understanding every corner case.

For tangible proof, this distributed transactions repository on my GitHub was built in just the last 6-8 weeks, showcasing the practical results of the knowledge gained:

GitHub Repository

I had a great learning experience with Arpit, the course helped me understanding the depth of system design.

For any problem statement how the approach should be, considering the trade off and what all should we consider, in a era where we have almost everything thing solved and easily available where we can pick the tool and solve the problem, this course helped in understanding why to choose something and where we can build our own

Thanks a lot

I have been following you and your work for more than 3 years now. Whenever I used to wonder about a problem statement, I would try to solve it myself and then explore about it. More often than not, I would find a post or a video at your youtube channel/Linkedin about it. Your posts always probed me to think harder and dive deep into the systems. Be it:

• databases

• algorithms

• or just data flows

I used to think that I go in depth about anything I read/work/do.. Until I discovered your work! It made me realise how deep the sea is actually and I was literally just scraping the surface in most of the things.

Coming to the course, I have been trying to take this course a few times. But something or the other always came up. This time I managed to prioritise it above everything else and I am so glad I did that. The systems discussed during this course have all been highly practical. Even though I had already read about some of them, I learned so many new things. In single speaker style courses, we cannot have the raw and different ideas that just comes up naturally in cohort style courses. It opens up so many dimensions for us to think.

Thanks a lot for sharing all the knowledge with us. I hope one day I would also be in a position to give back to the community. :)

Of all the system design courses I've taken, Arpit's stands out as the best by far. There are countless courses online, often taught by instructors with little to no real-world experience — many are fresh graduates who've never solved complex system problems in practice.

Arpit, however, is different. His experience as a Staff Engineer brings tremendous practical depth to every lecture. He doesn't just teach concepts — he dives deep into the "why" and "how," backed by real-world insights that only come from hands-on experience.

What also sets his course apart is the level of engagement he maintains with the cohort. The constant interaction and energy he brings keep everyone alert, curious, and actively learning.

I highly recommend this course to anyone looking beyond just interview preparation — this is for those who want to build lasting, real-world expertise and long-term career growth.

Best decision of my life and got so many pointer while designing system.

What I like about your teaching method is that you give chance each one of us to speak and navigate to the proper path. You always push us to THINK that ""you only engineer going to implement this system"" . You have increased my TODO list which I have already started working on this.

What you have covered from OS level like semaphore to large distributed system along with the Usecase. I would it say it is AsliEngineering.

Thankyou so much for this.

PS : I am missing ""Copy paste"" and Blah blah bhu bhu bee bee""