System requirements

Functional:

• Create a new link
• Access a generated link and redirect

Out of scope

• Authentication
• Expiration

Non-Functional:

• Heavy read
• Small write
• High availability
• Scalable (1 million DAUs, 10 million new links/day)
• Fast link retrieval (~200ms)

Out of scope

• Fault tolerance
• Data privacy
• Analytics

Capacity estimation

1 million DAUs

10 new links per user -> 10 million links/day generated

API design

POST /links -> Link object

Payload:

{

url: https://www.google.com

}

GET /links/{link_id} -> 301 redirect or 404 Not Found

Database design

Link

====

id: string

original_url: string

created_at: datetime

High-level design

User -> Load Balancer & API Gateway -> Link service -> Link table (postgres)

Link service -> Cached links (Redis key-value) and/or popular links (Redis sorted set)

Request flows

Explain how the request flows from end to end in your high level design. Also you could draw a sequence diagram using the diagramming tool to enhance your explanation...

Detailed component design

Dig deeper into 2-3 components and explain in detail how they work. For example, how well does each component scale? Any relevant algorithm or data structure you like to use for a component? Also you could draw a diagram using the diagramming tool to enhance your design...

Trade offs/Tech choices

Explain any trade offs you have made and why you made certain tech choices...

UUID vs Nanoid

Failure scenarios/bottlenecks

Try to discuss as many failure scenarios/bottlenecks as possible.

Future improvements

What are some future improvements you would make? How would you mitigate the failure scenario(s) you described above?