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So I'm reading through the WWDC slides from this year's excellent session "Optimizing Your App for Today’s Internet"https://developer.apple.com/videos/play/wwdc2018/714/I see some discussion of "optimistic DNS", and use of the kDNSServiceFlagsAllowExpiredAnswers flag.Is there any reasonable way to utilize this capability at the NSURLSession level? I don't see any documented high level API. Also, If I run DNS queries with the DNSService APIs & utilize this flag, will cached (and potentially expired values) get picked up by the higher level APIs?I understand the failover implications.