Why active checks
HTTPS probes give consistent availability evidence across hosting providers without installing visitor trackers or collecting user data. The fixed target list avoids exposing an arbitrary URL fetcher. Requests have bounded duration, bounded concurrency and no retained page content. TLS verification stays enabled, so certificate failures become availability failures rather than being hidden.
Measurement boundaries
Response time ends at arrival of HTTP headers, excluding full asset loading and rendering. Success means a 2xx response, not proof that every page feature works. Redirects intentionally fail the expected URL contract. Certificate lifetime describes the certificate served to this probe, which may differ across CDN edges.
Failure domains and missing samples
Both probes run from the local server and therefore share its internet and power dependencies. Grafana retains history independently, but a host outage produces a telemetry gap rather than evidence that both websites are down. Rolling availability covers observed scrape samples only; consult collection freshness before interpreting it. Multiple external locations would be needed for a stronger public availability objective.
Extensions
Connect hosting logs, deploy events, real-user performance or application metrics separately when access and a concrete investigation need exist. Do not label those signals as present until verified. Preserve the fixed label budget and never add visitor identifiers, URLs with query strings, or response content to metric labels.