System requirements

Functional:

• Given a long full url, it returns a short url
• Given the short url, it can redirct to the original address

Non-Functional:

• Reliability: the syste should be reliable for users to get/add urls
• Performance: it should be performant
• Scalability: it should be scalable with the increasing business need
• Cost: it should be cheap if possible

Capacity estimation

Assume we have

• 100M DAU, 1B peak users
• create short url 10/day and get short url 100/day
  • write 1000M QPD and read 10B QPD
  • 10k write QPS, 100k read QPS
• active time: 10yrs

API design

CreateTinyUrl:

• req:
  • full_url, string
• response:
  • short_url

GetFullUrl:

• req:
  • short_url, string
• full_url

Database design

url table

• url
• short_url
• long_url
• create_time
• expire_time

High-level design

Request flows

All the traffic goes

Detailed component design

The main difficulty is how to generate a uuid for the short url. We can use a short url with the length of 8 in base64. 64 ^ 8 = 2 ^ 48.

epoch in seconds: 100 * 365 * 24 * 60 * 60 = 3153600000 2 ^ 34

Trade offs/Tech choices

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?