Deequ
Deequ is an open-source library built on Apache Spark for defining 'unit tests for data' to measure data quality in large datasets. It allows users to specify constraints and metrics on their data, automatically verifying data quality at scale. The library is designed to work with data stored in distributed systems like Amazon S3, HDFS, or data warehouses.
Developers should learn Deequ when working with big data pipelines where ensuring data quality is critical, such as in data lakes, ETL processes, or machine learning workflows. It is particularly useful for automating data validation in production environments, helping catch issues like missing values, schema violations, or statistical anomalies early, which reduces errors and improves reliability in data-driven applications.