AWS Glue: The Complete ETL and Data Integration Guide

AWS Glue is a serverless data integration service that makes it easy to discover, prepare, and combine data for analytics, machine learning, and application development. Unlike traditional ETL tools that require infrastructure management, Glue handles the heavy lifting—you focus on your data transformations.
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AWS Glue is a serverless data integration service that makes it easy to discover, prepare, and combine data for analytics, machine learning, and application development. Unlike traditional ETL tools that require infrastructure management, Glue handles the heavy lifting—you focus on your data transformations.
Developer Professional (2025)
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The Data Catalog is Glue’s central metadata repository. Think of it as a Hive metastore on steroids—it stores table definitions, schemas, and partition information for all your data sources.
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Component Description Use Case Databases Logical containers for tables Organize tables by domain (sales_db, marketing_db) Tables Schema definitions pointing to data locations Define structure for S3 data, JDBC sources Crawlers Automated schema discovery Scan S3/databases and infer schemas Connections Network and credential configs Connect to RDS, Redshift, on-prem databases 2. Glue ETL Jobs
ETL jobs are where the transformation magic happens. Glue supports three job types:
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ETL jobs are where the transformation magic happens. Glue supports three job types:
Developer Professional (2025)
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A visual interface for building ETL pipelines without writing code. Drag-and-drop transformations that generate PySpark code behind the scenes.
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Here’s a production-ready Glue job that reads from S3, transforms data, and writes to Parquet:
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import sys from awsglue.transforms import * from awsglue.utils import getResolvedOptions from pyspark.context import SparkContext from awsglue.context import GlueContext from awsglue.job import Job from awsglue.dynamicframe import DynamicFrame # Initialize Glue context args = getResolvedOptions(sys.argv, ['JOB_NAME']) sc = SparkContext() glueContext = GlueContext(sc) spark = glueContext.spark_session job = Job(glueContext) job.init(args['JOB_NAME'], args) # Read from Data Catalog source_dyf = glueContext.create_dynamic_frame.from_catalog( database="sales_db", table_name="raw_orders", transformation_ctx="source_dyf" ) # Apply transformations # 1. Drop null values cleaned_dyf = DropNullFields.apply( frame=source_dyf, transformation_ctx="cleaned_dyf" ) # 2. Map columns to new schema mapped_dyf = ApplyMapping.apply( frame=cleaned_dyf, mappings=[ ("order_id", "string", "order_id", "string"), ("customer_id", "string", "customer_id", "string"), ("amount", "double", "order_amount", "decimal"), ("order_date", "string", "order_date", "date") ], transformation_ctx="mapped_dyf" ) # 3. Convert to Spark DataFrame for complex transformations df = mapped_dyf.toDF() df = df.filter(df.order_amount > 0) df = df.withColumn("year", year(df.order_date)) df = df.withColumn("month", month(df.order_date)) # Convert back to DynamicFrame output_dyf = DynamicFrame.fromDF(df, glueContext, "output_dyf") # Write to S3 as partitioned Parquet glueContext.write_dynamic_frame.from_options( frame=output_dyf, connection_type="s3", connection_options={ "path": "s3://my-bucket/processed/orders/", "partitionKeys": ["year", "month"] }, format="parquet", transformation_ctx="output" ) job.commit()Glue Crawlers: Automated Schema Discovery
Crawlers scan your data sources and automatically infer schemas. Here’s how to set one up with Terraform:
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Crawlers scan your data sources and automatically infer schemas. Here’s how to set one up with Terraform:
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resource "aws_glue_crawler" "orders_crawler" { database_name = aws_glue_catalog_database.sales_db.name name = "orders-crawler" role = aws_iam_role.glue_role.arn s3_target { path = "s3://my-bucket/raw/orders/" } schema_change_policy { delete_behavior = "LOG" update_behavior = "UPDATE_IN_DATABASE" } schedule = "cron(0 6 * * ? *)" # Run daily at 6 AM configuration = jsonencode({ Version = 1.0 Grouping = { TableGroupingPolicy = "CombineCompatibleSchemas" } }) }Glue Data Quality
Glue Data Quality (DQDL) lets you define and enforce data quality rules:
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Glue Data Quality (DQDL) lets you define and enforce data quality rules:
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# DQDL Ruleset Example Rules = [ ColumnExists "order_id", ColumnExists "customer_id", IsComplete "order_id", IsUnique "order_id", ColumnValues "order_amount" > 0, ColumnValues "order_date" between "2020-01-01" and "2025-12-31", Completeness "customer_id" >= 0.95 # 95% must have values ]Performance Optimization
1. Choose the Right Worker Type
Worker Type vCPU Memory Use Case Standard 4 16 GB General workloads G.1X 4 16 GB Memory-intensive, 1 executor/worker G.2X 8 32 GB Large datasets, complex joins G.4X 16 64 GB ML workloads, huge datasets G.8X 32 128 GB Extreme memory requirements 2. Enable Job Bookmarks
Job bookmarks track processed data to avoid reprocessing:
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Job bookmarks track processed data to avoid reprocessing:
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# Enable bookmarks in job config job.init(args['JOB_NAME'], args) # Read with bookmark support source_dyf = glueContext.create_dynamic_frame.from_catalog( database="mydb", table_name="orders", transformation_ctx="source", # Required for bookmarks! additional_options={ "jobBookmarkKeys": ["order_date"], "jobBookmarkKeysSortOrder": "asc" } )3. Pushdown Predicates
Filter data at the source level to reduce data scanned:
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Filter data at the source level to reduce data scanned:
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source_dyf = glueContext.create_dynamic_frame.from_catalog( database="mydb", table_name="orders", push_down_predicate="year=2024 and month=12" # Only read this partition )Glue Workflows: Orchestrating ETL Pipelines
For complex pipelines with multiple jobs, use Glue Workflows:
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For complex pipelines with multiple jobs, use Glue Workflows:
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📊 Example Workflow:
- Trigger: S3 event (new files in raw bucket)
- Crawler: Discover schema of new files
- ETL Job 1: Clean and validate data
- ETL Job 2: Aggregate and transform
- ETL Job 3: Load to Redshift
Cost Optimization
- Use Auto Scaling: Let Glue automatically adjust workers based on workload
- Optimize DPU Hours: More workers ≠ faster jobs (diminishing returns)
- Enable Flex Execution: Lower-cost option for non-urgent workloads
- Monitor with CloudWatch: Track DPU utilization to right-size jobs
Glue vs. Alternatives
Feature AWS Glue EMR Athena Serverless ✅ Yes ❌ No (Serverless EMR exists) ✅ Yes ETL Focus ✅ Primary use case ⚡ Flexible ❌ Query only Data Catalog ✅ Built-in ⚡ Uses Glue Catalog ⚡ Uses Glue Catalog Best For Batch ETL, Data prep Complex Spark/Hadoop Ad-hoc queries Further Reading
🎯 Pro Tip: Start with Glue Studio for visual pipeline building, then export the generated code to customize. This gives you the best of both worlds—quick prototyping with full code control.
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🎯 Pro Tip: Start with Glue Studio for visual pipeline building, then export the generated code to customize. This gives you the best of both worlds—quick prototyping with full code control.
Developer Professional (2025)
- 🎯 Pro Tip: Start with Glue Studio for visual pipeline building, then export the generated code to customize. This gives you the best of both worlds—quick prototyping with full code control.
Best Practices”,mastering-aws-api-gateway-a-comprehensive-guide/” style=”color:#0073aa;text-decoration:none;”>AWS API Gateway: REST APIs
Jennifer Walsh
Author & Expert
Senior Cloud Solutions Architect with 12 years of experience in AWS, Azure, and GCP. Jennifer has led enterprise migrations for Fortune 500 companies and holds AWS Solutions Architect Professional and DevOps Engineer certifications. She specializes in serverless architectures, container orchestration, and cloud cost optimization. Previously a senior engineer at AWS Professional Services.
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