def store(url, links):
    """write the URL, the links, and a UTC timestamp into the database."""
    db.delete_many({'url': url})  # remove all records for this URL
    db.insert({'url': url, 'links': links, 'createdAt': dt.datetime.utcnow()})
write the URL, the links, and a UTC timestamp into the database.
app/query_cache.py