Looks like there was an issue ongoing.
<a href="https://downdetector.com/status/aws-amazon-web-services/" rel="nofollow noreferrer">https://downdetector.com/status/aws-amazon-web-services/</a>
Our RDS instance suddenly became unresponsive to queries at ~11:30 am ET. Not sure if related, but haven't been able to find a cause yet and DB is hanging when trying to reboot. Strange b/c we can login to the DB, but querying any table, including postgres internal tables, hangs indefinitely.