Art of Codeartofcode
Lesson 12 of 21

1. How to Approach a Design Question

1
The picture to keep in your head
2
1.1 What is a system design interview, and what isn't it?
3
1.2 What is the interviewer actually scoring?
4
1.3 What's the step-by-step framework?
5
1.4 How do you manage a 45-minute round?
6
1.5 What questions should you ask first?
7
1.6 What's the difference between functional and non-functional requirements?
8
1.7 What's an API, and why define it before drawing boxes?
9
1.8 How do you sketch the data model?
10
1.9 What does a good high-level design look like?
11
1.10 How do you choose what to deep dive into?
12
1.11 How do you talk about trade-offs?
13
1.12 What if you get stuck or don't know something?
14
1.13 What are the most common mistakes?
15
1.14 What does the bar look like: fresher vs SDE-2?
16
Memory card and where the analogy breaks
17
Practice: five levels
18
Interview questions
19
Solutions
20
Sources
21
Code lab
1. How to Approach a Design Question

1.11 How do you talk about trade-offs?

3 min read+10 XP

At the architect's desk: "I gave you big windows because you wanted light. The cost is that the room heats up in summer. Unless you'd rather stay cool, then I'd use smaller windows and a skylight." The family trusts her because she names the downside herself.

In the interview: Every design choice gives something and takes something. A trade-off is saying both out loud. Use one sentence pattern:

"I chose ___ because ___. The cost is ___. Unless ___, in which case I'd switch to ___."

A real one from the URL shortener:

"I'll return a 302 (temporary) redirect because every click then passes through our servers, so we can count clicks. The cost is more traffic to our servers than a 301 (permanent) redirect, which browsers can remember and skip us on repeat clicks. Unless analytics doesn't matter, in which case a 301 cuts our load."

You don't need a trade-off for every box. Do it for the big decisions: the database, the caching, consistency, and anything the interviewer questions.

Memory code: "Because, Cost, Unless." Every big choice gets all three.