Fabrikam's web app relies on a CDN for static assets. They must cache responses separately when the 'q' query parameter changes, but ignore transient 'sessionid' query parameters when determining cache keys. They also want automatic origin failover if the primary origin is unhealthy. Which Azure CDN configuration satisfies these requirements?

The correct option directly addresses both requirements. Azure CDN caching rules allow for precise control over cache keys. By configuring a custom cache key to "include specified query strings: q" and implicitly excluding others, the CDN will cache responses separately for different 'q' values while ignoring 'sessionid'. Origin groups are the standard and recommended way to configure automatic origin failover in Azure CDN, ensuring high availability. The incorrect options fail for various reasons: "Ignore query string" would prevent caching based on 'q'. Setting a single origin with larger probe intervals does not provide automatic failover. "Include all query strings" would cache based on 'sessionid', which is explicitly not desired. Configuring multiple origins without origin groups does not enable automatic failover. Azure Front Door is a separate service, and while it offers advanced routing, the question specifically asks for an Azure CDN configuration. Relying on Front Door to strip 'sessionid' and then having CDN cache based on the full URL (which would still include 'q') is an overly complex and indirect solution for the given requirements, and not a direct CDN configuration.