Documented from https://cloud.google.com/monitoring/api/v3/metrics#time-series
Metric data is collected on schedules that vary across monitored resources. Some data is regularly "pulled" by Stackdriver Monitoring from the monitored resources, and some data is "pushed" by applications, services, or the Stackdriver Monitoring agent.
I'd like to know how stackdriver collects data from Google Cloud Pub/Sub, what is the promised latency bound? I've tried creating a topic/subscription and publishing messages and watch how long until the metrics logged in stackdriver. On average it's about 1-2 minutes, but sometimes very slow, up to 5-8 minutes.