
Glue connects to the external RDBMS (secured via JDBC + SSL and Secrets Manager), crawls schemas, and runs an ETL job that extracts tables to S3, converting to partitioned Parquet. Redshift loads from S3 via `COPY` into staging, then merges into modeled fact/dim tables with appropriate distribution and sort keys. A daily workflow (Glue Triggers/Step Functions) drives extract → transform → load, supporting incremental upserts and simple row-count checks.