URL shortening service

Use Cases

1, shortening : take a URL => return a much shorter URL

2, redirection : take a short URL => redirect to the original URL

3, custom URL : http://goo.gl/Trump2016

4, High availability

5, Analytics :

6, Automatic link removal

7, Manual link removal : e.g. porngraphy

8, UI vs. API, see http://goo.gl

Constraints:

make some guess about the volume

1, new URLs per month : 100 million   => because twitter daily tweets:

2, request per month : 1 billion =>

3, 10% for shortening and 90% for redirection

4, Requests per second : 400+ (40 : shortens, 360 : redirects)

5, 500 bytes per URL

6, 6 bytes per hash

Abstract Design:

1, Application service layer - services the requests

* shortening service

* redirection service

2, Data storage layer - keeps track of the hash<->URL mapping

* Acts like a big hash table

Bottlenecks:

1, traffic - how much, estimation, probably not the problem

2, data volume - quickly look up and insertion

3, how to split (scale)