Data Preparation on AWS: Comparing ELT Options to Cleanse and Normalize Data

Comparing the features and performance of different AWS analytics services for Extract, Load, Transform (ELT)

Gary A. Stafford
14 min readFeb 25, 2022


According to Wikipedia, “Extract, load, transform (ELT) is an alternative to extract, transform, load (ETL) used with data lake implementations. In contrast to ETL, in ELT models the data is not transformed on entry to the data lake but stored in its original raw format. This enables faster loading times. However, ELT requires sufficient processing power within the data processing engine to carry out the transformation on demand, to return the results in a timely manner.


As capital investments and customer demand continue to drive near hyper-growth of the cloud-based analytics market, the choice of commercial and open-source tools for data processing and data analysis seems endless. Even the major Cloud Service Providers (CSPs) have reached a point where they now offer multiple analytics services to accomplish similar tasks.

This post will examine the choice of analytics services available on AWS capable of performing ELT. Specifically, this post will compare the features and performance of AWS Glue Studio, Amazon Glue DataBrew, Amazon Athena, and Amazon EMR using multiple ELT use cases and service configurations.

Data pipeline architecture showing a choice of AWS ELT services

Analytics Use Case

We will address a simple yet common analytics challenge for this comparison — preparing a nightly data feed for analysis the next day. Each night a batch of approximately 1.2 GB of raw CSV-format healthcare data will be exported from a Patient Administration System (PAS) and uploaded to Amazon S3. The data must be cleansed, deduplicated, refined, normalized, and made available to the Data Science team the following morning. The team of Data Scientists will perform complex data analytics on the data and build machine learning models designed for early disease detection and prevention.

Sample Dataset

The dataset used for this comparison is generated by Synthea, an open-source patient population simulation. The high-quality, synthetic, realistic patient data and…



Gary A. Stafford

Area Principal Solutions Architect @ AWS | 10x AWS Certified Pro | Polyglot Developer | DataOps | DevOps | Technology consultant, writer, and speaker