&gt; Do you have to re-write your apps or is it upgradable<p>Looks like a fairly painless upgrade according to <a href="http:&#x2F;&#x2F;edgeguides.rubyonrails.org&#x2F;upgrading_ruby_on_rails.html#upgrading-from-rails-4-2-to-rails-5-0" rel="nofollow">http:&#x2F;&#x2F;edgeguides.rubyonrails.org&#x2F;upgrading_ruby_on_rails.ht...</a>