System requirements

Functional:

List functional requirements for the system (Ask the chat bot for hints if stuck.)...

A user can send a long URL and receive a short URL back

Non-Functional:

List non-functional requirements for the system...

Response time should be less than 200ms

System should be reliable

Capacity estimation

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

1m DAU

2 short URLs per day.

each of the URLs is accessed around 50 times per day.

Assuming each long url and short url cost 100 bytes.

Storage per year, 1M * 2 * 400 * 100Bytes = 80GB

Redirect requests per second will be approximate 100 million / 100,000 seconds = 1000 redirects per second.

API design

Define what APIs are expected from the system...

Generate a short URL

Post /v1/short-url

Body {originalUrl : "the original url", "Expire month" : 2}

Response 201 for success. 400 for error. If success, the response body will be the generated short url.

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...

id bigserial primary key,

original_url varchar not null,

short_url varchar not null,

expire_month int,

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...

1. Client: Initiates requests to either shorten a URL or request a redirect.
2. API Gateway: Manages client requests and directs them to the appropriate service (Shortening or Mapping). This also provides DDoS protection and can do TLS termination.
3. Shortening Service: Handles URL generation requests. It creates mappings of long URLs to short URLs in the database, and updates an in-memory or distributed cache for quick access.
4. Mapping Service: Handles redirect requests. It first checks the cache for the short URL mapping. If not found, it will query the database. The service responds with the redirection URL.
5. Cache: A key-value store, like Redis, provides fast access to frequently used mappings to speed up redirection requests.
6. Database: A scalable NoSQL database like DynamoDB stores all mappings in a more persistent form, ensuring data consistency and availability.
7. Service Response: Directs the output of cache/database lookups back to the client.

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?