What is the purpose of the load_ts column in this query, and how does it differ from transaction_ts?

load_ts is an ETL load timestamp that records when the row was ingested into the data warehouse. It is independent of the business event time captured in transaction_ts. The transaction_ts represents the actual time the transaction occurred at the point of sale. In many data pipelines, transaction_ts is used for business logic and reporting, while load_ts is used for data freshness, incremental load detection, and troubleshooting. For example, if you run a nightly batch that loads new rows, load_ts will be the same for all rows loaded that night, whereas transaction_ts will vary by the actual transaction time. Using load_ts you can identify late‑arriving data, perform change data capture, or roll back a load if needed. In contrast, transaction_ts is the primary key for time‑series analysis, trend calculations, and forecasting. Therefore, load_ts is a housekeeping column, whereas transaction_ts is a business column. When designing the schema, it's common to keep both columns. The load_ts can be used in downstream processes to filter out rows that were loaded before a certain point, or to detect duplicates. It also helps in auditing and compliance, as you can trace when data entered the system. In summary, load_ts is the ETL timestamp, transaction_ts is the business event timestamp.