The search functionality is broken, it seems, e.g. https://meta.stackexchange.com/search?q=test only loads after more than a minute of waiting. This happens on multiple sites, e.g. also on Stack Overflow.
One of the nodes in our primary Elastic cluster has been having a few issues (we suspect a hardware issue at this point) that have resulted in it randomly re-allocating shards across nodes. For, as yet, unknown reasons it drastically degrades cluster performance resulting in timeouts and intermittently taking the entire cluster offline. We're in the process of increasing capacity in that cluster as well as provisioning a replacement search node for the one that keeps blipping.
For the moment we've moved search traffic over to our failover cluster while the capacity increase and replacement nodes happen in the primary cluster. It'll be a bit slower but won't completely break like before :)
Apologies for the inconvenience!