A key component of our data lake is how we set up the zones or buckets. The popular approach is to implement a multi-hop data architecture which allows us to deal with stages of data quality at each hop or zone.
Extract Transform Load (ETL) vs Extract Load Transform (ELT)
One key difference exists when making the paradigm shift from traditional ETL to ELT. Traditional ETL bakes the transformation step into the middle of the extraction and loading process. This leads to ongoing maintenance costs and fragility since any changes require rewriting complex transformation logic code. ELT delays the transformation step until all data is loaded from the source system to the data lake destination. Benefits include: enabling continuous data loading, allowing as-needed application of transformations for analysis, eliminating break/fix maintenance, and facilitating the building of failure-proof data pipelines.
The Lake Data Quality Zones
Landing
Sometimes, this additional landing pre-raw-zone is needed to work out extra complex ELT logic depending on the source system integration.
Raw
Land the data here; this is raw and volatile to failure. No modification is made to the data here and it can be reprocessed. If you consider brittle ETL processes, many data quality issues related to infrastructure, schema changes, breaking jobs, etc. are isolated to this zone and remediated here. It is highly desirable to stick to an ELT pattern in data pipelines.
Stage
The data are typically translated from the raw formats and extracted files to an optimized columnar format, like parquet. Typically, some light scrubbing and de-duplication are done at this stage. These data are in a data quality state of “usable” and ready for downstream consumption. These data provide a single version of the truth from which all downstream data wrangling flows. Automation of both data quality rules and privacy controls can be implemented in this zone. Examples include standardizing to common date formats and PII detection/remediation for compliance.
Analytics
The terminal data quality zone in the data lake is the analytics zone. Aggregated and curated datasets live here. This is an ideal location to save and share curated datasets. Data stewardship, managing folder locations, permissions, and sharing for datasets can be implemented in this zone.
Addressing Automation and Data Quality Processing
The AWS Glue family of services includes tools to discover, integrate, prepare, clean, and transform data at any scale. ELT processing can be built with serverless glue data transformation activities as part of automated continuous data pipelines. Keeping our data moving and as fresh as possible through the quality zones in the data lake is critical. Additional operational features can be added such as feedback loops, SLA monitoring, and alerts on pipelines feeding the lake.
Additional activities for data quality handling in the lake can include:
- Data lake data quality layers IAM roles & permissions
- Creating data quality rules
- Handling schema evolution
- Implementing rejected records handling
- Managing lifecycle policies
- Using machine learning to address record matching
- AI services like Amazon Macie for sensitive automated data detection and protection
Once ELT pipelines that continuously process data from raw to stage zones are in place, the next steps are governance, stewardship, metadata management, and enabling the self-service capability for data wrangling.
Using AWS Lake Formation, the data steward will set up the following:
Data Stewardship for Self-Service Enablement
Data stewards manage permissions and control metadata tagging and grouping of tags into categories, often referred to as taxonomies and ontologies in metadata management.
- Configure workspace
- Configure user access
- Configure tagging and classification ontologies (PII, PHI, HIPAA, GDPR, Data Masking)
- Setup publishing
- Assign sharing permissions
The key to enabling self-service is the existence of a centralized metadata catalog combined with a vital data governance stewardship function. With AWS Lake Formation, companies can set up centralized data governance on top of their data lakes. Self-service tools like Amazon Athena and AWS Glue DataBrew and Amazon SageMaker Data Wrangler are used to clean and prepare data sets for analytics and machine learning. These tools connect directly to AWS Lake Formation’s centralized data catalog for querying and analysis. Cleansed datasets are saved to the analytics zone; metadata is saved to the catalog.
The above approach connects knowledge workers to a continuous feed of trusted data. This means faster answers to business-critical questions. In gold mining, the more paydirt is moved through an efficient refining process, the more gold is recovered. Let us help you kick-start your “data refinery!”
Caylent’s data engineering experts will work with you to build a foundational data lake and enable your teams to use no-code solutions for wrangling and exploring your data. Our Serverless Data Lake Caylent Catalyst will shorten your time to market from months to weeks and set you up to grow your data lake easily by scaling ingest sources through low-code solutions.
Brian Brewer
