AMPEL schematic for the live processing of ZTF alerts. External events, above dashed lines: This includes ZTF observations, processing, and the eventual alert distribution through the DiRAC center. Finally, science consumers external to AMPEL receive output information. This can include both tools for transient vizualisation (“front-ends”) as well as alerts through e.g., TNS or GCN. A set of parallel alert processors examine the incoming Kafka Stream (Tier 0). Accepted alert data are saved into a collection, while states are recorded in another. A light curve analysis (Tier 2) is performed on all states. The available data, including the Tier 2 output, are examined in a Tier 3 unit that selects which transients should be passed out. This particular use case does not contain a Tier 1 stage.