I understand that CSV files are coming into an S3 bucket. What changes are needed to handle this situation?

First, enable S3 event notifications on the bucket to trigger a Lambda function whenever a new CSV arrives. The Lambda can invoke an AWS Glue job or an EMR step that reads the file, applies a predefined schema, and writes the data to a target location (e.g., a partitioned Parquet dataset). To handle schema changes, use Glue's schema registry or a custom schema evolution strategy: detect new columns, add them to the target schema, and backfill missing values. Partition the data by date or source to improve query performance. Finally, set up monitoring with CloudWatch to track ingestion failures and use SNS or SQS for alerting. This pipeline ensures reliable, automated ingestion of CSVs into S3 while accommodating schema evolution.