System requirements

Functional Requirements

• create a short_url from a long_url; short_url should be 6 chars long
• be redirected to the original long_url from the short_url

Non-Functional Requirements

• low latency on redirects
• read-heavy; reads outnumber writes 10:1
• ensure uniqueness of short_url
• high availability, eventual consistency for URL shortening

Capacity estimation

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

API design

// get short_url from long_url

POST /urls -> short_url

{

long_url

}

// redirect to long_url from short_url

GET {short_url} -> Redirect to long_url

Database design

Use a key-value store like DynamoDB

• simple data; no need for complex relationships
• faster than relational DB b/c no additional latency for ACID compliance

TABLE urls

short_url

long_url

created_time

High-level design

Client

• request short_url from long_url
• go to short_url; should redirect to long_url

Server

• map short_url to long_url
  • save in database
  • return short_url to client
• retrieve long_url from short_url for redirects
  • query DB for short_url key

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...

Server

• possible implementations of url mapping
  • random + base62
  • hash + base62
  • counter

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?