title: Increase speed of CouchDB's _changes feed while applying a filter
body: <p>I'm having trouble with poor performance on CouchDB's <code>_changes</code> feed when there are multiple observers.</p>
  
  <p>I have CouchDB running inside a virtual machine on a laptop, and multiple iOS clients are consuming <code>_changes?feed=continuous</code> on one of the databases over the network, using CouchDB's HTTP API. As the number of clients increases, the speed at which the changes come through is slowed to a crawl.</p>
  
  <p><em>N.B. I'm actually communicating with CouchDB via an Apache reverse proxy, which is compressing the responses.</em></p>
  
  <p>And I'm also noticing that, while applying a filter to the feed, it will often go long periods without delivering any changes to the HTTP stream. Almost as if I'm waiting for it to check a batch of documents that don't meet my filter.</p>
  
  <p>Is there anything settings I can enable or optimisations I can make that will help speed this all up?</p>