>For us, latency means the time between when the _event_ actually occurs in real life (user clicks on a button) and when it showed up in all of our analytics integrations (Mixpanel, Intercom, etc.). As developers, this is the definition of "latency" that really matters for us because it represents the minimum time before we can take action on our users' behaviors.

This. I call it "end-to-end latency" and it doesn't get nearly as much attention as it should. This is, by the way, why it's a bad idea to use most OLAPs (like Redshift) as a backend for Segment if you want "real-time" analytics. Column-oriented OLAPs are not designed for real-time ingest because either they don't support streaming inserts (Redshift) or it's not particularly reliable (BigQuery).