def judge_probe(request):
    newest = max(request.probes, key=lambda p: p.probed_at)
    age = (request.now - newest.probed_at).total_seconds()
    if age < 0:
        return ["probe-future-dated"], None
    failures = []
    if age > request.probe_max_age_seconds:
        failures.append("probe-stale")
    return failures, int(age)
