defaultBatchThrottleQPS   = 10               // Limit the send rate by 10 QPS.
	defaultBatchThrottleBurst = 15               // Allow up to 15 QPS burst.
)

func appendBackend(existing, newBackend audit.Backend) audit.Backend {
	if existing == nil {
		return newBackend
	}
	if newBackend == nil {
		return existing
	}
	return audit.Union(existing, newBackend)
}