Stack:

Python 2.4 (will work fine on 2.7 with simplejson module installed)
BeautifulSoup
flup
Nginx
Werkzeug
Beaker

=== Running in Dev mode ===

OS X:

$ easy_install werkzeug
$ easy_install beautifulsoup
$ easy_install simplejson
$ easy_install beaker
$ easy_install pymongo

$ ./shortly.py
 * Running on http://127.0.0.1:8080/
 * Restarting with reloader

Now you can check that web service is working.
From another terminal tab:

$ curl http://127.0.0.1:8080/shortly/56320
[["E3", "Chiswick ", "5 min"], ["E3", "Chiswick ", "14 min"], ["E3", "Chiswick ", "19 min"]]

=== Deploying in production ===

You should follow Werkzeug instructions depending on your web server setup:
http://werkzeug.pocoo.org/docs/deployment/

If you choose to go with FastCGI setup you could use shorly.fcgi script included in the repository.