title: using a 301 redirect to maintain SEO
body: <p>I'm currently using freindly_id gem in a rails application to slug URLs and make them look nice. So rather than the URL #root/cities/1234 they are #root/cities/#cityname</p>
  
  <p>We are looking to change the cityname part of the URL to something else and it seems as direct as changing the slug in the database to simply read something else, however, someone has suggested we must use a 301 redirect in order to maintain the SEO we have acquired thus far. </p>
  
  <p>Can anyone tell me if there is an impact in changing the URL with the slug, as from my perspective it would seem that the URL is essentially not really changing, e.g. the underlying URL remains /cities/1234</p>