AWS’s Zero-ETL integration between Amazon RDS/Aurora and Amazon Redshift simplifies analytics by automating data replication, but it comes with specific challenges and limitations. Here are key issues to consider based on the [official documentation](https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/zero-etl.html ) and real-world use:
1. Limited Source/Target Support
– Sources: Only Aurora MySQL 3 (MySQL 8.0+) and RDS for MySQL 8.0.28+ are supported (as of 2025). No PostgreSQL, SQL Server, Oracle, etc.
– Targets: Exclusively Redshift Serverless or RA3 instances. Classic Redshift (DC2/DS2) isn’t supported.
2. Data Latency
– Near-real-time ≠ real-time: Data typically appears in Redshift within seconds to minutes, but this isn’t guaranteed for sub-second use cases.
– Batching: Changes are replicated in micro-batches, which may cause delays during low activity periods.
3. Schema & Data Type Constraints
– No Schema Customization: The Redshift schema mirrors the source 1:1. You can’t exclude columns, rename tables, or merge data from multiple sources.
– Unsupported Data Types: Certain types (e.g., spatial/geospatial data, large binary objects (BLOBs), or custom types) may not replicate or require workarounds.
– Schema Changes: Altering source tables (e.g., adding columns) requires careful coordination to avoid replication failures.
4. Transformation Limitations
– Zero-ETL ≠ Zero-Transform: Data lands in Redshift *untouched*. Complex transformations (joins, aggregations, cleansing) still need to be handled downstream via materialized views or scheduled queries.
– No On-the-Fly Processing: Unlike traditional ETL, you can’t apply transformations *during* replication.
5. Security & Compliance Complexities
– Encryption: Both source (RDS/Aurora) and target (Redshift) must use AWS KMS keys. Managing keys across services adds overhead.
– Network Isolation: Requires VPC peering or AWS Transit Gateway, complicating network architecture.
– Audit Gaps: Monitoring replication status requires correlating logs from RDS, Redshift, and CloudWatch.
6. Cost Implications
– Redshift Serverless Costs: Auto-scaling can lead to unpredictable costs if query patterns spike.
– Data Transfer Fees: Replication incurs cross-service data transfer charges.
– Storage Duplication: Data is stored in *both* RDS/Aurora and Redshift.
7. Operational Challenges
– Failure Handling: Replication can break due to schema conflicts, unsupported DDL, or network issues. Debugging requires checking both RDS and Redshift logs.
– Backup/Restore Complexity: Restoring a source database doesn’t auto-sync Redshift. You may need to reset the Zero-ETL link and reload data.
– Limited CDC Control: No access to raw CDC logs; replication is managed entirely by AWS.
8. Feature Gaps
– No Data Filtering: Replicates entire tables—no row/column filtering.
– Multi-Region Limitations: Cross-region replication isn’t natively supported.
– Max Tables/DBs: Default limits apply (e.g., 50 linked databases per Redshift instance).
When to Avoid Zero-ETL
– Complex Transformations Needed: If heavy data cleansing or merging is required pre-load.
– Multi-Source Analytics: Combining RDS data with non-RDS sources (e.g., DynamoDB, S3).
– Legacy Databases: Using unsupported engines (PostgreSQL, SQL Server, etc.).
– Strict Cost Control: Unpredictable Redshift Serverless costs may be prohibitive.
Alternative to Zero-ETL
Chat based data engineering tool Ask On Data is worth looking at. It addresses the shortcoming of this
- Ask On Data can support various kind of datasources including flat files, databases, API, Google Sheets etc.
- Ask On Data can support structured, semi structured and unstructured data sources.
- It can help in achieving things like joins, transformations, merging, calculations etc which is not possible in Zero-ETL
- No new coding language required. Everything is AI powered and chat driven.
- Unlike ZeroETL, AskOnData can be used by anyone including technical and non technical users.
- Multi source supported
- Predictable cost with costing depending on the usage.
- Strong auditing and logging capabilities
Reach out on support@askondata.com for free trial, POC.