Advanced System Design Fundamentals
The advanced companion to System Design Fundamentals, for senior engineers who have to choose between defensible options, defend the choice, and then operate what they built. Decision-first rather than component-first.
Course Overview
This course assumes you can already explain what a load balancer, a cache, a replica and a message queue do, and it starts where that knowledge stops. Every chapter is built around a judgment call a senior engineer actually faces: which storage engine, how much coordination, what to migrate and in what order, what to spend, what to bound, and what not to build at all. Each lesson gives you the options, what each one costs, and the condition that would make you change your mind, then closes with what an interviewer is really scoring. The course ends with three deliberately ambiguous end-to-end designs, worked against the same rubric a real interviewer uses.
What you'll learn in Advanced System Design Fundamentals
- Choose between two defensible designs and defend the choice with its cost and its revisit condition
- Size a design to the team that has to operate it rather than to the largest scale you can imagine
- Design messaging that survives duplicates, reordering and a consumer that has fallen behind
- Model data from access patterns, and recognize a partition key that will become a hotspot
- Run a zero-downtime migration with dual writes, a backfill, verification and a cut over
- Put a number on a design, find the line that dominates the bill, and name the cheaper option
- Set objectives and burn-rate alerts that page a human for a reason, and make a system debuggable
- Treat retrieval, inference and agents as search and capacity problems rather than model problems
- Scope an underspecified problem out loud, and say what you are deliberately not building
- Pick a storage engine, an isolation level and a sharding key from the workload rather than from habit
- Know when coordination is genuinely required, and remove it everywhere it is not
- Evolve a running system with expand and contract, strangler routing and reversible steps
- Go multi-region without trusting a standby that has never been promoted
- Bound a blast radius, shed load deliberately, and stop retries from amplifying an outage
- Threat model your own design, scope its secrets, and enforce tenant isolation in the database
- Run the forty-five minutes, recover from a wrong turn, and close with what you left out
Course Content
Database Internals and Scaling
Storage Engines: B-Trees vs LSM-Trees
MVCC and Isolation Levels in Practice
Replication: Lag, Failover, and Split-Brain
Connection Pooling and the Database Thundering Herd
Sharding in Practice
When Postgres Stops Being Enough
Exercise: The Postgres Primary at Its Limit
Chapter Assessment: Database Internals and Scaling
Monoliths and When to Split Them
SLOs, Alerting, and Incident Response
RAG, LLM Inference, and Agents
Running the 45-Minute Interview
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About the Author
Arslan Ahmad
Industry Expertise & Leadership
Arslan Ahmad is the lead author of Advanced System Design Fundamentals. As the founder of Design Gurus and a former FAANG hiring manager, he has worked at industry giants like Facebook (now Meta) and Microsoft.
He has conducted hundreds of system design interviews, giving him unique insight into what top tech companies look for in candidates.
The course also incorporates expertise from senior engineers at Google, Meta, Amazon, Microsoft, and Uber, ensuring you learn system design best practices from professionals who have built and scaled real-world systems.
500+
Interviews Conducted
10k+
Students Taught
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FAQs
Who is this course for?
It is for engineers who already know what a cache, a replica and a queue do, and who now have to choose between them, defend the choice in a review, and operate the result. If you are preparing for a senior system design interview, or you have just become the person who decides, it is written for you.
How is this different from System Design Fundamentals?
Fundamentals teaches the components. This course starts after that and is organized around decisions rather than parts, so every chapter is a judgment call and every lesson gives you the options, what each one costs, and the condition that would make you change your mind.
Do I need to take Fundamentals first?
Not formally, but you should be comfortable explaining load balancing, caching, replication and message queues before you start. The lessons here do not re-teach those, and the time saved goes into the trade-offs instead.
Is this only useful for interviews?
No. Every chapter is written to serve both the interview and the system you run on Monday morning, so the migration playbook, the cost model, the alerting rules and the failure drills are the same material you would use at work.
Is there any practice, or is it only reading?
Every chapter ends with an adaptive assessment that draws a fresh sample from a larger bank, so repeating it gives you different coverage rather than the same questions again. Every lesson also carries a flashcard deck for the facts worth recalling without reference, and several chapters include a worked exercise.
What does the capstone involve?
Three deliberately under-specified end-to-end designs: taking a single-region system multi-region under a cost ceiling, rebuilding a billing pipeline without losing or double-charging a transaction, and designing the first two years of a startup with five engineers. Each one is scored against the same rubric a real interviewer uses.
Does it cover AI systems?
Yes, as systems rather than as models. Retrieval is treated as a search and ranking problem, inference as a capacity problem with an unfamiliar unit, and agents as workflows that need durable state, idempotent actions and bounded loops.
Which technologies does it name?
It names specifics wherever a specific matters, including Postgres storage and isolation behavior, Kafka delivery semantics and consumer groups, Raft and etcd, DynamoDB and Cassandra partition limits, and pgvector index types. The reasoning is portable, and the figures are there so you can check them.
How long does it take?
About twenty-two hours of focused reading. The capstone exercises take longer if you work them properly, which is the intended way to use them.
Will it tell me which architecture is correct?
No, and that is deliberate. Most questions worth asking have several defensible answers, so the course teaches you to present the options, choose one, say what it costs, and name what would make you revisit it.
Does it assume a particular company size?
It targets senior roles at startups and scale-ups, so the constraints are a small team, a real budget and a system that already exists. Where advice from very large companies does not transfer, the lessons say so and give the small-team version.
