Simple Sinatra + Mongoid URL shortener (untested)

Gemfile

source 'https://rubygems.org'

gem 'sinatra'
gem 'slim'
gem 'mongoid'
gem 'bson_ext'

mongo_urlshortener.rb

require 'rubygems'
require 'bundler'

Bundler.require

configure do
  Mongoid.configure do |config|
    config.sessions = {
      default: { hosts: %w[localhost:27017], database: 'urlshortner' }
    }
    config.raise_not_found_error = false
  end
end

class Shorten
  include Mongoid::Document
  include Mongoid::Timestamps::Created

  field :url,      type: String
  field :shorten,  type: String
  field :count,    type: Integer,  default: 0

  index({shorten: 1}, {unique: true, name: 'shorten_id'})
end

get '/' do
  @shortens = Shorten.desc(:created_at).limit(10)
  slim :index
end

post '/create' do
  @shorten = Shorten.find_or_create_by(url: params[:shorten][:url])
  @shorten.shorten ||= Shorten.count.to_s(36)
  @shorten.save

  redirect "/#{@shorten.shorten}/info"
end

get '/:id' do |id|
  @shorten = Shorten.find_by(shorten: id)
  redirect '/' unless @shorten

  @shorten.inc(:count, 1)
  redirect @shorten.url
end

get '/:id/info' do |id|
  @shorten = Shorten.find_by(shorten: id)
  redirect '/' unless @shorten

  slim :info
end

__END__
@@layout
doctype html
html
  head
    title Sinatra and MongoMapper Url Shortener
  body
    == yield
@@index
form action="/create" method="post"
  div
    label for="url"
      | URL:
    input#url type="url" placeholder="http://" name="shorten[url]"
  div
    input type="submit" value="Submit"
    input type="reset" value="Clear"
#list style="margin-top: 20px;"
  - @shortens.each do |shorten|
    div
      span.url style="margin-right: 50px;"
        a href="/#{shorten.shorten}"
          = shorten.url
      span.count style="margin-right: 50px;"
         = shorten.count
      span.info style="margin-right: 50px;"
        a href="/#{shorten.shorten}/info"
          | Info Page
@@info
div
  p: URL: #{@shorten.url}
  p: Shorten URL: http://#{request.host}/#{@shorten.shorten}
  p: Created at: #{@shorten.created_at}
  p: Count: #{@shorten.count}