Increasing Performance

Do you think it could be a slowdown with your server rather than against the Drupal stack?

If you want to optimise it “as much as possible”, Drupal is probably out of the question, at least for the AJAX callback. If you use Drupal for that, it will have to be bootstrapped for each AJAX request separately before there is anything sent to Solr. While certainly not easy, bypassing this has a huge potential for performance gains, which I don't think you'll be able to get otherwise.

It doesn't get much faster than Pantheon when you're running Drupal. Maybe this function isn't possible in Drupal, as per comment #3.

Yes, you even get JSON back (and with a well-defined structure) so handling this in Javascript should be trivial. The query also shouldn't be too hard to setup. The main work will probably be theming the results in JS.
However, I don't think you'll be able to contact the Solr server directly via AJAX. Firstly, the browser's same-origin policy might prevent you from doing that, even though it's just the port that's different. Secondly, your Solr server would have to be accessible from the outside for that, which I'd strongly discourage. This would effectively eliminate all security on the Solr server, people would be able to make arbitrary queries on it and even (the really bad part) add, edit or delete documents in your index.

So, there's probably no avoiding a small script on your web server that passes the query on. But since that could be almost trivial (just a pass-through for request and response, with a few safety checks) and even implemented directly in C with CGI, that probably won't make any real difference performance-wise.

Well, first off you should make sure that only the /select handler can be reached this way – any access to /update should of course be prohibited. Other than that, the restrictions would (as far as I can see) just be the ones imposed by your application – e.g., if you have unpublished nodes indexed which normal users shouldn't see, be sure to always pass a bs_status:true filter. The downside of circumventing Drupal is of course the lack of authentication (unless you choose it's worth the performance penalty and additional work to somehow still access the login information), so you can't display more content to admins (or other special groups) than to normal users.

If you write a php script,can you post it here or as a module?

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