Take Home Exercise (Backend)

Problem

Write a server that acts as a bit.ly-like URL shortener (as a JSON API)

Goals

• Be able to generate arbitrary shortened urls (e.g. bit.ly/2FhfhXh) such that:
  • the same input url outputs the same shortened url (i.e. it's deterministic)
• Be able to create a custom short link urls (e.g., bit.ly/my-custom-link)
• Handle the actual redirect from short url → original url
• Be able to return the following stats about a given short url to the api consumer:
  • When the link was created
  • Total number of visits
  • A histogram of the total number of visits per day

Future Goals (Extra Credit)

• Deploy the server to an accessible URL
• Number of “unique” visitors to a given shortlink (you can define how we track visitors)
• A “global stats” endpoint, that aggregates some interesting stats across your URL-shortening platform (e.g., total number of links/visits per domain, histogram of total visits across the site)

Non-Goals

• Try to predict/foresee what features we'd want to add to this system
• Handle more than one custom url (could be a future goal)

Design

Overview

• Programming Language: Go
• Libraries: There are web frameworks like gin and echo, but that seems like. I'd rather stick to more lightweight router library to keep things simple, minimize dependencies, etc. Let's try gorilla/mux
  • Note: Of course there are other libraries I'll find handy too for things like CLI flag parsing, error handling, etc. but no need to flesh those out here
• Data Store: Don't have much experience in NoSQL databases, but a KV store feels like a natural fit (the original url as key, json blob as value). I've always wanted to tinker with Redis, so I'll start with this db driver (over others mainly because the repo seems more active)

Sample Usage

Setup

## run local redis server (reset if necessary)
redis-cli flushall
redis-server

## run the server (new tab) localhost:8080
go run .

Shortening Some URLs

## create a short url at localhost:8080
curl -d '{"url": "https://google.com/", "custom_suffix": "goog"}' -H 'Content-Type: application/json' localhost:8080/shorten/

{
    "original_url": "https://google.com/",
    "default_url": "cwe8WeI6myY",
    "custom_url": "goog",
    "metadata": {
        "CreatedAt": "2021-12-13T17:58:06.578754-05:00",
        "visits": 7,
        "encoded_hist": "SElTVEZBQUFBREY0MnBKcG1Tek13TURBd3NEQXdNakF3TURLQUFLTWJRdEFWT0w5bUgvMkg4QWlERy9ibVBrQUFRQUEvLytIL3dmRg=="
    }
}

## go to the url in browser (or directly using curl)
curl localhost:8080/goog/

<a href="https://google.com/">Found</a>.

curl localhost:8080/cwe8WeI6myY/
<a href="https://google.com/">Found</a>.

Getting Some Metadata

## pretty some basic stats (histogram is an encoded object)
curl localhost:8080/cwe8WeI6myY/stats/

{
    "created_at": "0001-01-01T00:00:00Z",
    "visits": 9,
    "encoded_hist": "SElTVEZBQUFBREY0MnBKcG1Tek13TURBd3NEQXdNakF3TURLQUFLTWJRdEFWT0w5bUgvMkg4QWlERy9ibUlVQUFRQUEvLytJQXdmSg=="
}

## see histogram as csv in stdout (for easy import elsewhere)

cat histogram.csv

[...]
2021-12-07T19:44:48-05:00,2021-12-08T13:57:03-05:00,0
2021-12-08T13:57:04-05:00,2021-12-09T08:09:19-05:00,0
2021-12-09T08:09:20-05:00,2021-12-10T02:21:35-05:00,0
2021-12-10T02:21:36-05:00,2021-12-10T20:33:51-05:00,0
2021-12-10T20:33:52-05:00,2021-12-11T14:46:07-05:00,0
2021-12-11T14:46:08-05:00,2021-12-12T08:58:23-05:00,0
2021-12-12T08:58:24-05:00,2021-12-13T03:10:39-05:00,0
2021-12-13T03:10:40-05:00,2021-12-13T21:22:55-05:00,9