Hi, I would like to point you to a discussion on the DNS-OARC mailing list: https://lists.dns-oarc.net/pipermail/dns-operations/2018-December/018196.htm... One of the operators at .ca noticed that old probes report way higher response times using DNS CHAOS queries (300% or more) (see also [3]). After some digging, we came to the conclusion that this has to do with the fact that he is carrying out “one-off” measurements. When carrying out the same query for a longer time, we cannot observe this delay. The issues seems to be that one-off measurements are scheduled at probes using a different library than measurements that run for a longer period (“eooqd” instead of “eperd”). Some small additional delays have been documented before on the RIPE Atlas website and in research papers [1, 2], but the big delay with one off measurements was new to me. Also to others? Is our assumption correct that the scheduler is the culprit? Moritz [1] https://dl.acm.org/citation.cfm?doid=2805789.2805796 [2] https://clarinet.u-strasbg.fr/~pelsser/publications/Holterbach-ripe-atlas-sh... [3] https://atlas.ripe.net/measurements/18086197/#!probes