System requirements

Functional:

• Create short URL for long URL
• Redirect users with short URL to long URL
• Authenticate user
• Analytics for shorten URL
• User generated short URL
• Manage deleted URLs

Non-Functional:

• Availability: System needs to be high available
• Scalability: System needs to be able to handle high traffic for redirection
• Consistent: All users should be able to use the short URL for redirection. After shortening, long URL update should be consistent for all users

Capacity estimation

URLs to shorten - 200/sec

Redirection traffic - 20000 redirects/sec

Avg size of long URL - 2KB

Avg size of short URL - 256B or 0.256KB

User metadata: 5KB

Total data to be stored - 200 * 60 * 60 * 24 * 10KB = 172 GB per day

API design

shortenURL()

input: long URL, user id

output: short URL

redirect()

input: short URL, user id

output: redirection to long URL

Database design

Use key value store like dynamodb for strong consistency and scalability for large amount of data

High-level design

Client

• Sends request for redirection or creation of short URL

API gateway

• Handles request routing
• Implements rate limiting

Shortening service:

• Handles URL shortening(hashing)

Redirection Service:

• Redirects user with short URL to long URL

DynamoDB:

• Stores long-short URL pair

Cache:

• Store frequently accessed URLs
• Improves read performance and reduces latency

Request flows

Shorten URL: Client sends long URL for shortening. Service shortens URL. Store long-short URL in DB and update cache

Redirect: Client sends request with short URL. Access short URL from cache. If not present in cache, get it from database

Detailed component design

Trade offs/Tech choices

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

Failure scenarios/bottlenecks

Future improvements

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