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How to Cover the Lessons
On This Page
- The shape of the fortnight
- Where the two hours go
- The 45 minutes
- The 20 minutes that matter most
- When you fall behind
- The second pass
This course is 30 problems across 14 days. That is a real pace, and it only works as a routine. Reading it like a book does not stick.
The previous lesson, The 14 Step Framework, covers what to do inside one problem. This lesson covers the clock and the calendar: how long to spend, what to do each day, and what to do on the days it goes wrong.
1. The shape of the fortnight
One theme per day. Twelve of the days have two problems. Day 6 and Day 7 have three, so expect those two to run long.
The themes move from the apps you use every day toward the infrastructure you never see. Day 1 is content delivery, which is YouTube and Netflix. Day 14 is coordination, which is a lock manager and a job scheduler. By the time you reach the systems nobody demos, you already know why they exist.
The pairing inside each day is deliberate. YouTube sits next to Netflix. WhatsApp sits next to Discord. Redis sits next to DynamoDB. Each pair looks like the same problem and gets a different answer, and the reason for the difference is the actual lesson.
2. Where the two hours go
| Block | Time | What happens |
|---|---|---|
| Problem A | 45 minutes | One full pass, using the three moves below |
| Problem B | 45 minutes | The same three moves |
| Compare the two | 20 minutes | Why did today's two problems choose differently? |
That is 110 minutes. On Day 6 and Day 7 the third problem takes it to about two and a half hours. Those are the two days worth protecting in your calendar in advance.
3. The 45 minutes
Split each problem into three equal blocks. Same three every time, so it becomes automatic.
First 15 minutes: frame it. Sections 1 to 4. Read the scope and the requirements, then do the estimates yourself before you read ours. Getting a number wrong and finding out why is worth more than reading the right one.
Next 15 minutes: design it. Sections 5 to 7. Read the API and the data model, then cover the screen and draw the architecture on paper. If you cannot draw it, you have not understood it yet, and you have just found that out in 15 seconds rather than in an interview.
Last 15 minutes: trace it. Section 8. Walk one write and one read all the way through your own drawing. This is the section that separates people who have read about systems from people who can talk about them.
Sections 9 to 14 are for the second pass. Skim them the first time. Coming back to them later is far more useful than grinding through them now.
4. The 20 minutes that matter most
Most people skip this part. It is the highest value 20 minutes of the day.
Put the day's two problems side by side and ask why they diverged:
- WhatsApp and Discord are both chat. Why does one route through a session cache and the other through a queue?
- YouTube and Netflix both stream video. Why does one pull content to the edge and the other push it there overnight?
- The shopping cart and the stock exchange are both write paths. Why does one refuse to ever reject a write and the other refuse to ever reorder one?
Memorising 30 designs is not the goal, and it will not survive contact with a question you have not seen. Recognising which constraint forces which answer is what transfers.
5. When you fall behind
You will miss a day. Plan for it now rather than treating it as failure.
- Skip, do not stall. A missed day is not a failed course. Carry on with today's theme and come back.
- Halve the day. One problem done properly beats two skimmed. Drop the second, keep the comparison for the weekend.
- The order is not sacred. The days are grouped by theme, not built on each other. If Day 9 interests you more today, do Day 9.
The only version of this that fails is the one where a missed Tuesday turns into a missed fortnight.
6. The second pass
The first pass builds recognition. The second builds recall, and recall is what an interview actually tests.
Give a problem 20 minutes rather than 45, and change what you do:
- Cover the page and draw it from memory. Then open the lesson and mark what you missed. What you missed is your study list.
- Now read sections 9 to 14. Caching, scaling, failure and security land properly once the shape of the system is already in your head.
- Say the design out loud for five minutes. Interviews are spoken. Talking through a design is a different skill from understanding it, and the only way to practise it is to talk.
Two weeks gets you through the material. The second pass is what makes it yours.
Let's get started.
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On This Page
- The shape of the fortnight
- Where the two hours go
- The 45 minutes
- The 20 minutes that matter most
- When you fall behind
- The second pass