EugeneTeu / url-shortener

for govtech TAP

url-shortener

url: (over http) http://35.232.1.32:8080/

URL Shortener Tech Design

Background

• User want to be able to submit any url so that it can be shortened and used / shared
• Backend api server to handle conversion of a given url
• Frontend app that allow user to submit a request to convert a url andd print converted URL
• Store url in Relational database

I have chosen the following technology to code this application in

• NodeJs (Express)
• React
• Typescript
• MySQL

Schema

CREATE TABLE url_service.URL (
  hash varchar(256) NOT NULL,
  converted_url varchar(256) NOT NULL,
  original_url varchar(512) NOT NULL ,
  created TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (hash)
);

• Each url is uniquely identified by their hash
• If multiple users submit the same url, it will be stored as different hashes

System Architecture

The following documents the overall architecture of the system

package "Backend Express server" {
  [Client App (react)]
  [API server]
}


database "database" {
  [url_service]
}

[Client App (react)] -> [API server]
[API server] -> [url_service]

---

• BE Serves FE on a single VM instance in google cloud

API Design

• POST BASE_URL/url

Request	Response Format
{"url" : string}	{ "url": string}

Generating Hash Logic

• Method to generate Hash

export function hashUrl(originalUrl: string, seqNumber: number): string {
  const md5Sum = crypto.createHash("sha256");
  const digest = md5Sum.update(originalUrl + seqNumber + "").digest("base64");
  return digest;
}

export function getShortKey(hash: string): string {
  if (hash.length < 9) {
    return undefined;
  }
  return hash.slice(0, 9);
}

• Takes in the single user string and a unique sequence number
• Hashes against SHA256 and encode it in base64
• Takes the first 8 characters of the string (gives us 64^8 unique strings)
• Stores this hash as the primary key.
• unique sequence number to handle case where 2 users submit the same url to be converted, the api behaviour will return valid shortened links for both users that are unique!