System requirements

Functional:

receive long URL, return shortened url

receive shortened URL, redirect to long url

need to persist for 30 days

Non-Functional:

should be highly available (aka fast)

Capacity estimation

100s of users per minute

tens of thousands of records per day

API design

REST

shorten

retrieve

Database design

one table

columns:

original url, shortened url, created_at

primary key would be shortened url since that's what we'll be querying by

expiring records?

would use sql, but could use nosql since it's so simple.

High-level design

Request flows

Pretty simple. only two possible types of request, basically a save and retrieve.

save will take long url, generate. short url, then return it to the client

retrieve will take short url, map it back to long, and redirect

Detailed component design

Trade offs/Tech choices

wanted to keep this as simple as possible. no need for users or auth

Failure scenarios/bottlenecks

extremely high use could bog it down.

many stale URLs, could be cleaned up

Future improvements

add periodic cleanup logic or expiration

could have multiple instances and a load balancer,

rate limiting to prevent abuse