Changed the outbound firewall rules for our production server. And suddenly it couldn't speak to MngoDB Atlas. We definitely had rules to allow mongo traffic bu

Changed the outbound firewall rules for our production server. And suddenly it couldn't speak to MngoDB Atlas. We definitely had rules to allow mongo traffic but still somehow it wasn't working . We noticed every time a connection to mongo was being made some connections were also going to a CDN on port 80. Looked pretty suspicious until we discovered it was just OCSP which verifies cert revocation status. So ultimately it was going to the cert issuer - letsencrypt who had issued mongo's cert.