Extract, load, transform

Extract Load Transform is an alternative to ETL used with Data Lake implementations. In ELT models the data is not processed on entry to the data lake which enables faster loading times. But does require sufficient processing within the data processing engine to carry out the transform on demand and return the results to the consumer in a timely manner. Since the data is not processed on entry to the Data Lake the query and schema do not need to be defined a-priori (often the schema will be available during load since many data sources are extracts from Databases or similar structured data systems and hence have an associated schema).

Many articles have been written comparing ELT and ETL such as the following:

• http://www.dataacademy.com/files/ETL-vs-ELT-White-Paper.pdf
• http://smartdatacollective.com/tamaradull/306046/data-lake-debate-pro-s-first