Data Engineering

A primary source is data you collect directly for the purpose (e.g., your app's events); a secondary source is data originally collected by someone else or for another purpose that you reuse.

The content (what fields/signal it carries) and the location (where it physically lives, e.g., S3 bucket, database, device).

Clickstream/app events, IoT device telemetry sensors, and application or server logs streamed in near-real time.

They are high-volume, automatically generated records of behavior and events, useful for anomaly detection, forecasting, and feature engineering without manual labeling effort.

A prefix is the string before the object key delimiter (the folder-like path). Prefixes organize data and historically affected request parallelism/partitioning of datasets.