Amazon RDS Optimized Reads is available by default on RDS for PostgreSQL versions 15.2 and higher, 14.7 and higher, and 13.10 and higher. This feature is now available on Intel-based M5d and R5d instances with up to 3,600 GiB of NVMe-based-SSD block-level storage and AWS Graviton2-based M6gd and R6gd database (DB) instances with up to 3,800 GiB of NVMe-based SSD block-level storage and up to 25 Gbps of network bandwidth. You can configure these disk based DB instances as Multi-AZ DB cluster, Multi-AZ DB instances, and Single-AZ DB instances. https://aws.amazon.com/jp/about-aws/whats-new/2023/04/amazon-rds-optimized-reads-2x-faster-queries-rds-postgresql/