System requirements

Functional:

1. **URL Shortening:**

  - The system should provide a mechanism to shorten long URLs.

  - Shortened URLs should be unique and not collide with existing ones.

2. **Redirection:**

  - When users access a shortened URL, they should be redirected to the original long URL.

  - The redirection process should be fast and seamless.

3. **Custom Alias:**

  - Users should have the option to customize their short URLs with a chosen alias (if available).

  - Alias should be unique across the system.

4. **Analytics:**

  - The system should track analytics, including the number of clicks, geographic location of clicks, and time of access.

  - Provide a dashboard or API for users to access these analytics.

5. **Expiration:**

  - Provide an option for users to set an expiration date for their short URLs.

6. **API:**

  - Offer a RESTful API to allow integration with other services and applications.

  - API should support URL shortening, retrieval, and analytics retrieval.

7. **Security:**

  - Implement security measures to prevent misuse and unauthorized access to short URLs.

  - Support HTTPS for secure data transmission.

Non-Functional:

1. **Scalability:**

  - The system should handle a large number of URL shortening requests and clicks.

  - Scalability should be achieved through horizontal scaling.

2. **Performance:**

  - The redirection process should be fast, with minimal latency.

  - Ensure that the system can handle concurrent access without performance degradation.

3. **Reliability:**

  - The service should be highly available and have minimal downtime.

  - Implement mechanisms for fault tolerance and disaster recovery.

4. **Storage:**

  - Efficiently store and retrieve a large number of short URLs and their associated data.

  - Use reliable and scalable storage solutions.

5. **Backup and Recovery:**

  - Regularly backup data to prevent data loss.

  - Implement a recovery process to restore data in case of failures.

Capacity estimation

Estimate the scale of the system you are going to design...

API design

Define what APIs are expected from the system...

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...

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?