System requirements

Functional:

• Shorten URL:the system should allow userst to submit

a long URL and receive a shortened URL

• Redirect: user should be able to access the original URL by visiting the shortened URL.
• Analytics: the system should provide users with statistics on the usage of their shortened URLs
• Custom aliases:user is able to create a shortened URL with a custom alias instead of a randomly generated one.
• Expiration : allow for URLs to have an expiration date,

after which they no longer work.

• User management:user is able to create account,log in, and mange their shortened URLs
• API Access:there should be an API that allows third-party applications to generate and retrieve shortened URLs.
• Link preview: When a user hovers over or clicks on the shortened URL, the system may provide a preview of the long URL.

Non-Functional:

• Scalability:The system should be able to handle an increasing number of requests as the user base grows. This might involve horizontal scaling and load balancing strategies
• Availability: The service should ensure high availability, aiming for an uptime of at least 99.9%.
• Performance: The system should respond to requests in a timely manner, ideally in less than a second for URL shortening and redirection.
• Security: Implement measures to prevent abuse, such as rate limiting and validation checks for URLs.
• Maintainability: : The system should be designed in a way that makes it easy to update, debug, and manage.
• Data Consistency: Ensure that the URL mappings are consistent across the database and cache.
• Logging and Monitoring:the system should have logging capabilities to track usage patterns, errors, and other performance metrics.

1. User Experience: the user interface should be intuitive, and the service should provide an API with clear documentation for developers.

Capacity estimation

• Total URLs Shortened = User Base * Average URLs per User
  • 1,000,000 users * 10 URLs = 10,000,000 URLs

• Total URL Accesses = Total URLs Shortened * Average Accesses per URL
  • 10,000,000 URLs * 100 accesses = 1,000,000,000 accesses

Storage Calculation:

In terms of database and storage:

• Assuming each shortened URL requires:
  • 20 bytes for the original URL
  • 10 bytes for the short code/alias
  • 10 bytes for metadata (e.g., creation date, user ID)

Total size per URL = 20 + 10 + 10 = 40 bytes

• Total Storage Required = Total URLs Shortened * Size per URL
  • 10,000,000 URLs * 40 bytes = 400,000,000 bytes or approximately 400 MB of storage

Bandwidth Estimation:

If we expect that each request to the URL shortening service would require:

• 1 KB of data (for the request and immediate response)
• Then for 1 billion accesses:
  • Total bandwidth = 1,000,000,000 accesses * 1 KB = 1,000,000,000 KB or approximately 1,000 TB of data transmitted.

API design

API Endpoints

1. Create Short URL
   • Endpoint: POST /shorten
   • Request Body:
   • { "longUrl": "http://example.com/some/very/long/url", "customAlias": "myCustomAlias" // optional}
   • Responses:
     • 201 Created:
     • { "shortUrl": "http://short.ly/abc123"}
2. Redirect Short URL
   • Endpoint: GET /{shortCode}
   • Responses:
     • 302 Found: Redirects to the long URL.
     • 404 Not Found: If the short code does not exist.
3. Get URL Analytics
   • Endpoint: GET /analytics/{shortCode}
   • Responses:
     • 200 OK:
     • { "shortUrl": "http://short.ly/abc123", "clickCount": 150, "createdAt": "2023-01-01T00:00:00Z", "lastAccessedAt": "2023-01-15T12:00:00Z"}
4. Update Short URL
   • Endpoint: PUT /shorten/{shortCode}
   • Request Body:
   • { "longUrl": "http://example.com/new/long/url"}
   • Responses:
     • 200 OK:
     • { "message": "URL updated successfully"}
     • 404 Not Found: If the short code does not exist.
5. Delete Short URL
   • Endpoint: DELETE /shorten/{shortCode}
   • Responses:
     • 204 No Content: Successfully deleted.
     • 404 Not Found: If the short code does not exist.

Flow of API Usage

To visualize the flow of using these APIs, consider the following sequence diagram:

sequenceDiagram

participant U[User] participant S[API Server] participant DB[Database] U->>S: POST /shorten S->>DB: Store longUrl and generate shortCode DB-->>S: Response with shortCode S-->>U: Return shortUrl U->>S: GET /{shortCode} S->>DB: Retrieve longUrl DB-->>S: Return longUrl S-->>U: Redirect to longUrl U->>S: GET /analytics/{shortCode} S->>DB: Get URL analytics DB-->>S: Response with analytics data S-->>U: Return analytics data

This diagram shows the interaction between the user, API server, and database during URL shortening, redirection, and analytics retrieval.

1. Caching Layer

• Improvement: Introduce a caching layer (like Redis or Memcached) to store frequently accessed shortened URLs.
• Benefit: This can reduce the load on the database and improve response times for redirects.

2. Advanced Analytics

• Improvement: Expand analytics capabilities to include:
  • Geolocation data (where users are accessing the URLs from).
  • Data on device type or browser used.
  • Referral sources to understand where traffic is coming from.
• Benefit: Provides users with detailed insights, potentially increasing user engagement.

3. Rate Limiting

• Improvement: Implement rate limiting per user or IP address to prevent abuse.
• Benefit: Safeguards the service against potential DDoS attacks or spamming of URLs.

4. Custom Alias Suggestions

• Improvement: If a user chooses a custom alias that’s already taken, offer suggestions for alternative aliases.
• Benefit: Enhances user experience by helping users find available options quickly.

5. URL Validation

• Improvement: Validate URLs to ensure they are correctly formatted and potentially harmful URLs can be flagged or blocked.
• Benefit: Improves security and helps prevent users from shortening harmful or malicious links.

6. User Dashboard

• Improvement: Create a user dashboard where users can see their shortened URLs, analytics, and manage their aliases.
• Benefit: Improves user engagement and allows users to manage their shortened URLs more effectively.

7. Mobile Optimization

• Improvement: Optimize the API and website for mobile usage or provide a dedicated mobile app.
• Benefit: Increases accessibility and user engagement from mobile users.

8. Setting Expiration for URLs

• Improvement: Allow users to set expiration dates for their shortened URLs.
• Benefit: Helps manage storage costs and ensures that outdated links are removed.

9. API Versioning

• Improvement: Implement API versioning to manage changes over time without disrupting existing users.
• Benefit: Ensures backward compatibility and a smoother transition for users when updates or changes are made.

10. Improved Security Measures

• Improvement: Implement OAuth or API keys for user authentication on the API.
• Benefit: Enhances security by ensuring that only authorized users can access or modify their URLs.

Database design

Defining the system data model early on will clarify how data will flow among different components of the system. Also you could draw an ER diagram using the diagramming tool to enhance your design...

High-level design

You should identify enough components that are needed to solve the actual problem from end to end. Also remember to draw a block diagram using the diagramming tool to augment your design. If you are unfamiliar with the tool, you can simply describe your design to the chat bot and ask it to generate a starter diagram for you to modify...

Request flows

Explain how the request flows from end to end in your high level design. Also you could draw a sequence diagram using the diagramming tool to enhance your explanation...

Detailed component design

Dig deeper into 2-3 components and explain in detail how they work. For example, how well does each component scale? Any relevant algorithm or data structure you like to use for a component? Also you could draw a diagram using the diagramming tool to enhance your 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?