I just happened to notice that the self, next and last links in the
Atom feed [1] are pointing at the wrong place:

<feed xmlns="http://www.w3.org/2005/Atom">
  <title>Library of Congress Subject Headings</title>
  <link href="http://id.loc.gov/subjects/feed/1" rel="self"/>
  <link href="http://id.loc.gov/subjects/feed/2" rel="next"/>
  <link href="http://id.loc.gov/subjects/feed/4117" rel="last"/>
  <id>info:lc/authorities/subjects/feed</id>
  ...
</feed>

should instead look like:

<feed xmlns="http://www.w3.org/2005/Atom">
  <title>Library of Congress Subject Headings</title>
  <link href="http://id.loc.gov/authorities/subjects/feed/1" rel="self"/>
  <link href="http://id.loc.gov/authorities/subjects/feed/2" rel="next"/>
  <link href="http://id.loc.gov/authorities/subjects/feed/4117" rel="last"/>
  <id>info:lc/authorities/subjects/feed</id>
  ...
</feed>

The same seems to be the case for the LCNAF feed [2] as well. Since
I'm on the subject, I've noticed that digging back in time seems to
take longer the further you go.

ed@taylor:~$ time curl --silent
http://id.loc.gov/authorities/subjects/feed/501/ > /dev/null
real	0m3.193s
user	0m0.004s
sys	0m0.008s

ed@taylor:~$ time curl --silent
http://id.loc.gov/authorities/subjects/feed/1001/ > /dev/null
real	0m12.031s
user	0m0.008s
sys	0m0.004s

ed@taylor:~$ time curl --silent
http://id.loc.gov/authorities/subjects/feed/1501/ > /dev/null
real	0m15.623s
user	0m0.004s
sys	0m0.008s

ed@taylor:~$ time curl --silent
http://id.loc.gov/authorities/subjects/feed/2001/ > /dev/null
real	0m22.023s
user	0m0.012s
sys	0m0.004s

ed@taylor:~$ time curl --silent
http://id.loc.gov/authorities/subjects/feed/2501/ > /dev/null
real	0m24.492s
user	0m0.004s
sys	0m0.008s

ed@taylor:~$ time curl --silent
http://id.loc.gov/authorities/subjects/feed/3001/ > /dev/null
real	0m27.716s
user	0m0.008s
sys	0m0.008s

ed@taylor:~$ time curl --silent
http://id.loc.gov/authorities/subjects/feed/3501/ > /dev/null
real	0m46.800s
user	0m0.008s
sys	0m0.008s

ed@taylor:~$ time curl --silent
http://id.loc.gov/authorities/subjects/feed/4001/ |less
real	0m1.225s
user	0m0.008s
sys	0m0.012s

I'm not sure if some optimizations can be made there. I guess the
silver lining is that Varnish appears to be caching the result, so
it's just the first person to request the URL that has to pay the
price.

//Ed

[1] http://id.loc.gov/authorities/subjects/feed/1
[2] http://id.loc.gov/authorities/names/feed/1