Design URL Shortening Service

Clarification questions

How the customer experience will looks like ?
- Customer may wants to use simple number and letters instead of symbols, special characters.
- Customer can create custom URL if they are willing to pay extra
- Customer can decide till when this shortened URL should exist ?

Total expected URLs : 1million, it can grow in future
- Let’s say, we use letter and numbers only
- 26 + 10 = 36 combinations we can used and url length can be 6,
- so total 36⁶ = 2 billions URLs system should handle.
Total expected redirections : 1 millions, it can grow in future
How may total users are there in systems ?
How may actives users on daily basis ?
How much is the storage will be required ?
- save original URL = 100 char
- shortend URL = 6 char
- Total Storage = (100+6) * 1 million new URLS = 100 million ~ 100 MB per day
- Yearly ~ 100 MB * 365 = 36500 MB = 36.5 GB
Transaction per second
- Write Request per day : 1 million new URLS
- Read Request per day : 10 million reads ~ 10 * 10⁶ Request ~ 10⁷
  - Seconds per day : 84000 ~ 10⁵
  - Transaction per seconds : 10⁷/ 10⁵ ~ 100 read request per second
- How many servers required
  - Single server can handle appoximately ~ 10000 requests
  - Servers = Transaction per seconds / 10000 = 100 / 10000 ~ 1 server

<Domain.com>:443/urlservice/v1/urls/create
- create – Post HTTP Method
  - Body
    - user_id
    - original_url
    - custom_output_url <optional shortened_url>
  - Response
    - user_id
    - original url
    - output_url <shortened_url>
  - ErrorCodes: 200 ok, 4xx not found, 5xx service down, service errors etc
<Domain.com>:443/urlservice/v1/urls/get?url=<shortened_url>
- get – Get HTTP Method
Header
- Authorization token (JWT token)
- Authentication system :
  - No need of login ?
  - OAuth (Off the shelves)
- Content type : json etc
- user_id

API Response time : Three 9’s availability is fine ~ 100 ms response time.
To decrease load on backend server (celebrity problem), we can introduce cache (Redis/memcached).
To reduce latency on customer’s point of view, if bugdet if available we can introduce CDN to cache hot URL’s in different geographical areas near to edge locations.