99.9% of requests to npm over the last 3 months have been hitting things other than couch. Binaries are being served directly from disk by nginx, and 99% of JSON GETs are served from our CDN's cache. Couch is still the source of truth, but we treat it much more like a database than an app these days, and it's been much more reliable that way. The only time you're really hitting couch directly these days is when you publish.

Almost none of our downtime since February (when we sorted out some bugs in our app that were affecting couch performance) is attributable to couch. Mostly it has been network-related problems at the caching layer, and the fixes we need to make involve making failover faster and more reliable, as failures are inevitable in any large distributed system.