Who This Course Is For

A system design round often starts with one line. Design a service that sends notifications to a hundred million users. Then the interviewer stops talking and waits for you.

There is no single correct answer to that question. There is a way to work through it. There are also choices you will be asked to defend. This course teaches both.

Who this course is for

This course is written for engineers preparing for senior interviews. That means Senior, Staff, and Principal roles. Many companies label these levels L5 and above.

You will get the most from it if these are true:

• You already know the basic parts. Load balancer, cache, message queue, replica, and shard.
• You can design a small system, but a broad and open question slows you down.
• You want to say why you chose something, not only name it.

If those parts are new, start with Grokking the System Design Interview. That course teaches the building blocks one at a time. This course assumes you have them.

What is inside

The course has four parts, and each one is used differently.

Twelve case studies. Each is a complete design. It runs from the first clarifying question through to the scaling plan. This is the main content of the course, and it is where you should start.

System design patterns. These are named solutions that appear in many systems. A write-ahead log, leader election, and quorum reads are three examples. Read them when a case study uses one you do not know.

Seven architecture studies. These describe how real systems were actually built: Dynamo, Cassandra, Kafka, Chubby, HDFS, GFS, and BigTable. They are the most detailed material here. They are useful once the case studies feel comfortable.

A final assessment. A question bank that draws from the whole course.

What this course does not do

It does not teach the fundamentals again. There is no lesson explaining what a load balancer is. Volume I teaches those basics, and repeating them here would waste your time.

It also does not give you a design to memorize. Interviewers change the problem as soon as they hear a rehearsed answer. They may add a region, remove a guarantee, or raise the traffic by a hundred times. What you reuse is the method, not the specific answer.

One more thing worth saying plainly. A senior interview is not scored on whether your design matches the one in this course. It is scored on whether you asked the right questions, made your assumptions visible, and defended your choices when pushed.

What you should be able to do at the end

By the end of the course you should be able to:

• Turn a one-line problem into a written list of requirements.
• Size a system with rough arithmetic before choosing any technology.
• Draw a high-level design and explain what every part is for.
• Name the trade-off behind each choice, and say what you gave up.
• Answer follow-up questions about failure and growth without starting over.

Key Takeaways

• This course is for Senior, Staff, and Principal interview preparation.
• It assumes you already know the basic building blocks of a system.
• The twelve case studies are the main content, so start there.
• The patterns and the architecture studies support the case studies. Read them as you need them.
• The goal is a repeatable method, not a set of designs to memorize.

The next lesson gives you a reading plan, based on how much time you have before your interview.