Q. How does the performance scale?
A. Linearly.  We can do one anonymity set globally every second.<p>Q. When an APT exfiltrates permutation data, what is the privacy failure mode?
A. It would be very difficult for an APT to penetrate all sites simultaneously to violate privacy.  It is also not clear that a single server would have access to the full permutation, as it can be MPC separated.