Requirements

Functional Requirements:

• create short url for a long given url
• reject url coming from the same domain
• editions are not allowed

Non-Functional Requirements:

• high availability
• data replication
• stateless services
• sharded storage

Capacity Estimation

• ~100M creations per day
• ~10B redirection per day

API Design

POST:/api/url

request: {url:string}

response: {shortUrl:string}

response_codes: 200, 422, 429

GET:/code

request: {code: string}

response_codes:

• 404,429
• 302
  • header: location

High-Level Design

• Infrastructure
  • LoadBalancer
  • Api Gateway
  • Cache
  • Database

Backend

• CreateUrlService (Validates and Creates the shortUrl)
  • ValidUrlChecker (Check if it is a valid url)
  • OwnUrlChecker (Check if it comes from our own domain)
  • UrlShortener (Generate a unique short code for the given url)
  • ExistentUrlChecker (Check if the url actually exists) (Optional)

• RedirectService (Fetches the original url based on the given code)

• ShortenedUrlRepository (Layer responsible to deal with cache and database needs. Deals with transaction to guarantee uniqueness)

Database Design

• cache (redis)
  • key:value
    • shortened_url:original_url
    • ttl : 1m
• database (mysql)
  • table
    • shortened_urls
      • original_url
        • varchar
      • shortened_url
        • varchar
        • unique index

Detailed Component Design