System Design Framework

Mindset

The design is less important than the actual collaboration works
- As no one expect you to design a real-world system within 1 hour
Let the interviewer knows what you're thinking, communicate with your interviewer
- Don't think in silence
Some of the skills that you need to demonstate
- Design skill
- Defend your design choice
- Respond to feedback in a constructive manner
If get stuck, dont hesitate to ask for hints
What the interviewer looking for
- Ability to
  - Collaborate
  - Work under pressure
  - resolve ambiguity constructively
  - ability to ask good questions
- Red flags
  - over-engineering
    - High cost
  - narrow mindedness
  - stubborness

Do not jump to a conclusion too early - huge red flags ^980869
Ask the right questions.
- What's the feature?
- How many users?
- How fast do we want to scale up (3 months, 6 months or a year)
- What exisiting services i can use to leverage the design
Make proper assumptions
- If making assumptions, write down in the piece of paper so that you remember later
Gather the information
- Understand the requirements
- Clarify ambiguities
Do back-of-envelope calculation

Note: treat your interviewer as a co-worker during the process

Come up with initial design, get some feedbacks
Draw simple diagrams
Suggest multiple solutions if possible
Go through some concret use cases to detect edge cases
- Ask if the interviewer needs API endpoints and database schema definition

Make sure before doing this step, you have:

Agreed on the overall goals and feature scope from step 2
Sketched out the high level design
Obtained the feedback from the high level design
- Had some ideas on which areas to focus on based on the feedback

For this one, you have to

Extend from the above design, for example in step 2 you have Fanout Service. in this step you can go into detail of that service

Never say it's perfect and nothing can be improved
- Always say there is always something to improve upon
Give a recap of your design
Error cases (server failure, network lost)
How to handle next scale, what if you have to handle 10 million users
Propose refinement if have time