Exam SSE-Engineer Topic 1 Question 21 Discussion

A burst logon event, where a large branch office population authenticates and begins generating DNS lookups within a narrow five-minute window, is exactly the scenario Prisma Access ' s DNS proxy sizing limits and caching behavior are designed to withstand, and understanding those documented defaults explains user- visible behavior during onboarding rushes like this one. The DNS proxy on Prisma Access caches every resolved record it handles, not merely a curated subset of " frequently used " hostnames, for a fixed default duration of 300 seconds; this blanket caching (option D) is precisely what allows a large burst of simultaneous, repeated lookups for the same common destinations (SaaS portals, internal domains, update servers) to be served from cache rather than generating a fresh upstream query for every single request, which is critical to sustaining performance during a synchronized-logon event. The DNS proxy also has a defined ceiling on how many TCP-based DNS requests it will hold pending concurrently, documented as 64 (option B); in a large burst scenario this is the throttling limit that governs how much simultaneous TCP DNS load the proxy will queue before applying back-pressure. Option A misstates the caching behavior - caching is not selective to " frequently used " hostnames, it applies broadly for the TTL period. Option C references a retry count that is not the documented, relevant limiting factor in this burst-capacity scenario.
Reference:Prisma Access - DNS Proxy Behavior and Default Sizing Limits.