Loading data into data marts
Many tools can work directly with data in the data lake, as we covered in Chapter 3, The AWS Data Engineer's Toolkit. These include tools for ad hoc SQL queries (Amazon Athena), data processing tools (such as Amazon EMR and AWS Glue), and even specialized machine learning tools (such as Amazon SageMaker).
These tools read data directly from Amazon S3, but there are times where a use case may require much lower latency, higher performance reads of the data. Or, there may be times where the use of highly structured schemas may best meet the analytic requirements of the use case. In these cases, loading data from the data lake into a data mart makes sense.
In analytic environments, a data mart is most often a data warehouse system (such as Amazon Redshift), but it could also be a relational database system (such as Amazon RDS MySQL), depending on the use case's requirements. In either case, the system will have local storage (often high-speed...