System requirements

Functional:

1. Given a long url, output a shortened url
2. shortened url only have 8 bytes for length
3. click on shortened url able to redirect to long url

Non-Functional:

1. availability
2. low latency, within 1second

Capacity estimation

1. 200K employees, 10 requests per day, 23 RPS, peak 100RPS
2. A simple server can easily handle 10K RPS, CPU wont be an issue
3. long url 1K bytes, short url 8 bytes, daily 2M * 1.1K = 2.2G, month 70G, year - 840G ~ 1T

API design

1. Get v1/shortenedUrl/longurl=?
2. Get v1/shortenedUrl return the webpage points to url

Database design

MySQL

save it within a table

add cache when read from database

High-level design

1. generate shortened url user -> loadbalancer -> urlshortner -> DB

1. resolve the shortened url, user, give out a shortened url -> resolver -> DB, then direct it to long url

Request flows

1. generate shortened url user -> loadbalancer -> urlshortner -> DB

1. resolve the shortened url, user, give out a shortened url -> resolver -> DB, then direct it to long url

Detailed component design

• url shortener, 8bytes has 64 bits. Url can be generated based on timestamp 42 bits, region id 5 bit, machine id 5 bits, sequence number 12bits
• shortened url resolver. Cache over the DB saves over the past 7 days generated urls. Key-value pair, given the shortened url, it maps it to the original url

Trade offs/Tech choices

1. url shortner can use other ways, like hash code of the long url, which is longer than 8 bytes
2. each url shortner should sync on time

Failure scenarios/bottlenecks

1. database is down.
2. for url generated a year ago, need to go through DB and fetch the original url which can be slow

Future improvements

1. improve the resolver time