# Limitations for the Amazon RDS Data API RDS Data API has the following limitations: + You can only execute Data API queries on writer instances in a DB cluster. However, writer instances can accept both write and read queries. + With Aurora global databases, you can enable Data API on both the primary and secondary DB clusters. However, a secondary cluster doesn't have a writer instance until it's promoted to be the primary. Data API requires access to the writer instance for query processing, even for read queries. As a result, read and write queries sent to the secondary cluster fail while it lacks a writer instance. Once a secondary cluster is promoted and has a writer instance available, Data API queries on that DB instance succeed. + Data API isn't supported on T DB instance classes. + For Aurora PostgreSQL version 14 and higher databases, Data API only supports `scram-sha-256` for password encryption. + The response size limit is 1 MiB. If the call returns more than 1 MiB of response data, the call is terminated.