Last time someone posted prerender.io on HN, I totally wasn’t ready. We only had the open source component. Launch early, right? Now, we’re a full blown SaaS solution for rendering HTML to crawlers from SPAs or AJAX heavy websites.
Our open source prerender server has improved a lot. We fully support _escaped_fragment_ and only check user agents for the crawlers that don’t support it. The server starts a pool of phantomjs processes, has a robust plugin architecture, can be installed via npm, and easily customized like expressjs.