Lets say you have a fragment of the page which displays the most recent posts, and you expire it in 30 minutes. I'm using Rails here.

```
<% cache("recent_posts", :expires_in => 30.minutes) do %>
  ...
<% end %>

```

Obviously you don't need to do the database lookup to get the most recent posts if the fragment exists, so you should be able to avoid that overhead too.

What I'm doing now is something like this in the controller which seems to work:

```
unless Rails.cache.exist? "views/recent_posts"
  @posts = Post.find(:all, :limit=>20, :order=>"updated_at DESC")
end

```

Is this the best way? Is it safe?

One thing I don't understand is why the key is "`recent_posts`" for the fragment and "`views/recent_posts`" when checking later, but I came up with this after watching `memcached -vv` to see what it was using. Also, I don't like the duplication of manually entering "`recent_posts`", it would be better to keep that in one place.

Ideas?