service/donate.md

@@ -212,7 +212,22 @@ sandbox client id and app secret)."
 
 ## Pager playbook
 
-TODO: how do we deal with high latency and exceptions?
+### High latency
+
+If the site is experiencing high latency, check
+[metrics](#monitoring-and-metrics) to look for CPU or I/O contention. Live
+monitoring (eg. with `htop`) might be helpful to track down the cause.
+
+If the app is serving a lot of traffic, `gunicorn` workers may simply be
+overwhelmed. In that case, consider increasing the number of workers at least
+temporarily to see if that helps. See the `$gunicorn_workers` parameter on the
+`profile::donate` Puppet class.
+
+### Errors and exceptions
+
+If the application is misbehaving, it's likely an error message or stack trace
+will be found in the [logs](#logs). That should provide a clue as to which parts
+of the app is involved in the error, and how to reproduce it.
 
 ### Stripe card testing