It is what lets a segment change this morning affect a message this afternoon, and what AI agents and next-best-action systems need to act on current context.

In practice

Batch-updated profiles quietly cap personalization. If the profile a campaign reads is a day old, so is every decision made from it. Measure the lag directly: fire an event, then time how long until it reaches the profile a campaign reads. Seconds is real-time; minutes to hours is batch wearing a real-time label.