System requirements

Functional:

• URL length should be 6-15 characters
• URL should be kept indefinitely
• Users will be redirected to the real url when visited the shortened one

Non-Functional:

• Monthly active users is 10 million
• Daily redirection usage is 1 million
• Daily url creation is 100,000

Capacity estimation

• TPS = 1 million per day / 24 hours / 3600 seconds = 12 TPS
• peak TPS = TPS * 2 = 24 TPS
• creation TPS = 1 TPS
• peak creation TPS = 2 TPS
• Daily storage = 100000 * 1kb = 1Gb
• Yearly storage = 400 Gb

API design

Create Short URL API

• PUT /v1/create?sourceUrl={}
  • HTTP Verb: PUT
  • Path: /v1/create
    • sourceUrl: string, input for the source URL
  • Response:
    • shortenedUrl: string, shortened URL
    • Example: https://short.io/visit?id=fjiadj2346

Redirect Short URL API

• GET /visit/id?={}
  • HTTP Verb: GET
  • Path: /visit
    • id: string, id for the source URL
  • Response:
    • Code 302 to redirect to the source URL
    • Source URL in string

Database design

NoSQL database storing the relationship between shortened url (id) and the source url

• id: unique id for the source url
• source_url: the original url

Example:

id source_url

fjiadj2346 https://meta.com

High-level design

• Clients: users of the application
• Load Balancer: Dispatcher of the incoming requests
• Server: host of the application
• Unique ID Generator: a component that generates a unique id
• Database: NoSQL database for storing the url relationship

Request flows

For URL creation:

1. Client sends requests to the backend
2. Load balancer receives the request and dispatches to application host
3. In the application hosts, the services calls the unique id generator to generate a uniqe identifier for the source url
4. Server then saves the relaltionship in a nosql database
5. Server responds success to the client with the shortened url

For URL redirection:

1. Client sends request to the service
2. Load balancer receives the request and dispatches to one of the application host
3. The application host looks up the id from the database and returns the source url back with status code 302
4. Clients receives the redirection response and gets redirected to the source url

Detailed component design

Trade offs/Tech choices

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

Failure scenarios/bottlenecks

Try to discuss as many failure scenarios/bottlenecks as possible.

Future improvements

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