Not who you are responding to, but really interesting comment, thanks!

I am not too knowledgeable on the topic, may I ask you what sort of confidence is required for a well working contact tracing application? A naiv those-who-live-together is so utterly useless that it was rejected? And do I get it right, you meant to real-time track everyone and if someone turns out to be infected, everyone gets quarantined who they met in the preceding days? What percentage of contacts can “slip through” so that it is still effective? Isn’t there a working trade-off like counting people who work together and family or is it still subject to unimplementable exponential explosion?

Or am I asking the wrong questions as these are epidemiologic ones rather than technical? If so, excuse my lack of knowledge on the topic.