TinyTrace

TinyURL

TinyURL
Table of Contents
Design
Structure
- Error Handling
Requirements

Design

General Architecture Diagram

Diagram

Load Balancers: distribute traffic accross multiple web instances
Session State: Use a NoSQL database to store session state
URL Shortener Service: Responsible for generating short URLs, storing URL mappings and retrieivng original URLs

Java Spring boot (Backend) Architecture Diagram

Spring Boot Security backend-security

React (Frontend) Architecture Diagram

react-component-diagram Context diagrams These diagrams are based on the idea of State Diagrams

front-end-auth-context-diagram front-end-url-context-diagram front-end-page-context-diagram

API Design

Public Endpoints

POST /api/auth/signup

Message properties | fields | Description | | :——— | :————————————————————– | | email | The user email address | | username | The username which has to be unique in database | | password | The user choice of password that has to meet certain conditions |

Response Properties
```
{
"jwt": {The generated jwt token for the user},
"_links": {
    "urls": {
        "href": {api/urls/{user-id}}
    }
}
}
```
Status code | fields | Description | | :—– | :——————————————– | | 400 | Validation failed: password not strong enough | | 409 | Username or email already taken |
POST /api/auth/login

Message properties | fields | Description | | :——— | :————————————————————– | | username | The username which has to be unique in database | | password | The user choice of password that has to meet certain conditions |

Response Properties
```
  {
  "jwt": {The generated jwt token for the user},
  "_links": {
      "urls": {
          "href": {/api/urls/{user-id}}
      }
  }
  }
```
Status code | fields | Description | | :—– | :———————————— | | 404 | Username does not exists | | 401 | Invalid credentials, invalid password |

GET /api/urls/{shortURLId}

Response Properties

  {
      "shortUrlId": {The shortUrlId generated by the shortener service},
      "longUrl": {The original longUrl given by the user},
      "userId": {User-id},
      "_links": {
          "self": {
              "href": {/api/urls/{user-id}}
          },
          "urls": {
              "href": {/api/urls}
          }
      }
  }

Status code | fields | Description | | :—– | :—————————————- | | 404 | Url withi this shortUrlId does not exists |

Authenticated Endpoints

POST /api/urls

Message properties | fields | Description | | :———– | :———————————————— | | shortUrlId | Blank, will be generated by the Shortener service | | longUrl | The long Url given by the user to shorten | | userId | The User Id |

Response Properties
```
  {
      "shortUrlId": {The shortUrlId generated by the shortener service},
      "longUrl": {The original longUrl given by the user},
      "userId": {User-id},
      "_links": {
          "self": {
              "href": {/api/urls/{user-id}}
          },
          "urls": {
              "href": {/api/urls}
          }
      }
  }
```
Status code | fields | Description | | :—– | :——————————- | | 400 | Validation failed, URL constrain |

GET /api/urls

Response Properties

  {
      "_embedded": {
          "urls": [
              {
                  "shortUrlId": {The shortUrlId generated by the shortener service},
                  "longUrl": {The original longUrl given by the user},
                  "userId": {User-id},
                  "_links": {
                      "self": {
                          "href": {/api/urls/{user-id}}
                      },
                      "urls": {
                          "href": {/api/urls}
                      }
                  }
              }
          ]
      },
      "_links": {
          "self": {
              "href": {The current HAL link}
          }
      },
      "page": {
          "size": {The size of each page},
          "totalElements": {The total number of URL links},
          "totalPages":  {The total number of pages}, 
          "number": {0-indexed page number}
      }
  }

Status code | fields | Description | | :—– | :————————————— | | 404 | Url with this shortUrlId does not exists |

DELETE /api/urls/{shortURLId}

Response Properties
```
  {
      "success": {Boolean, whether or not it was successful or not}
  }
```
Status code | fields | Description | | :—– | :————————————— | | 404 | Url with this shortUrlId does not exists |

Database Schema

I chose a NoSql design because of the high read-write requests that will be expected of the application. The only purpose of using a relational database for this application is the consideration of race-conditions where 2 users decide to shorten a longUrl with the shortening algorithm generating a similar shortUrlId (In the case of a distributed environment), the use of a relational database will be able to ensure consistency of data. However in a NoSql database this isn’t the case and could cause an issue. A point in consideration is to seperate the shortener service to a microservice that has its own independent relational database to generate the shortUrlIds.

er-diagram

Table URL, it’s possible to add more fields for metrics purposes, eg:
- clicks
- creation date

Shortening Algorithm

I chose to use a simple random generator for the shortUrlId with a backoff algorithm that will sent out an error just in case it took too long to generate a random shortUrlId.

I did not use a base conversion technique. While it make ensure uniqueness in the generation of the shortUrlId, the generation is in linear order and could be predictable. I didn’t use a hashing algorithm because of the possibility of a collision that could happen, while it is unlikely.

Structure

Error Handling

I chose to use @ControllerAdvice global exception handling instead of using ResponseStatusExcepion handling because I don’t want to fill my controllers with many try-catch blocks and I still find myself needing to create exception classes to handle different errors. ResponseStatusException goal was to try to fix this, but this is mainly for the same exception type but providing the flexibility of sending different status error code which doesn’t fit in my user.

Requirements

User Stories

As a user, I want to have a shorter URL so that I can have an easier time sharing links
As a user, I want to view a table of short URLs to long URLs so that I can keep track of which past URLs I have shortened
As a user, I want to be able to delete a short URL mapping
As a user, I want my short URL to be accessible to anyone so I can share with people
As a user, I want to be able to share my a QR code for my shortURL for easier accessbility

Non-Functional Requirements

Low latency (100ms)
High availability
Estimation
URL life: 10 years = 315.56 million seconds
1000 writes per second
10000 reads per second
Total unique URLs in 10 years: 315.56 $\times$ 1000 $=$ 31.5 billion
62 character set (alpha-numeric)
$62^7 = 3.52$ trillion (Use 7 characters to represent unique URLs)
Glossary

Resources

https://medium.com/gitconnected/system-design-interview-question-design-url-shortener-c3278a99fc35
https://medium.com/@sandeep4.verma/system-design-scalable-url-shortener-service-like-tinyurl-106f30f23a82
https://www.geeksforgeeks.org/system-design-url-shortening-service/
https://medium.com/homeday/how-does-it-feel-like-with-your-own-url-shortener-serverless-service-5fce0dd1bbec

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