Zscaler Digital Experience (ZDX) uses web probes to measure application performance from the user’s perspective. Official ZDX reference material and EDU/ZDTE study guides describe the four key web-probe metrics as Page Fetch Time (PFT), DNS Time, Server Response Time (Time to First Byte), and Availability. These same metrics are explicitly called out in training and exam prep as the values that can be used when defining application-level alert rules (for example, “DNS Time > X ms” or “Server Response Time > Y ms”).
ZDX documentation also explains that each alert rule type (Application, Device, Network, or Call Quality) has its own metrics and criteria, and that application alerts are driven by web-probe metrics like DNS Time and Server Response Time, while network alerts use CloudPath metrics such as latency and packet loss. Because both DNS Time and Server Response Time are application-probe metrics, they can legitimately be used together as criteria in an application-type alert rule.
By contrast, combinations that mix web-probe metrics with network-only metrics (like Packet Loss Rate) or vaguely defined “Network Response Time” do not reflect how ZDX structures its alert criteria per type. Therefore, among the listed options, the pair that correctly represents valid ZDX alert criteria for application monitoring is DNS Time and Server Response Time.
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