RDS Serverless v2, Postgresql 15.4 high idle cpu

RDS Serverless v2 operates with a minimum capacity threshold, which you've configured at 0.5 ACUs. This means you're continuously billed for this baseline capacity, regardless of database activity. Unlike some serverless computing services that can reduce costs to zero during idle periods, RDS Serverless v2 maintains a constant minimum resource level to ensure rapid response times and consistent database availability. The 50% CPU utilization you're observing could be attributed to various factors such as background processes, routine maintenance, or the specific way RDS calculates and reports utilization for Serverless instances. It's essential to recognize that Serverless v2 is optimized for specific use-cases, such as applications with variable workloads or multi-tenant systems. If your application has a steady, predictable workload, Serverless v2 may not be the most cost-effective solution, as it will consistently utilize CPU, memory, and IOPs resources.

When configuring your Minimum and Maximum ACUs, several factors need consideration. The AWS documentation provides detailed guidance on this: https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/aurora-serverless-v2.setting-capacity.html

It's crucial to align your ACU settings with your actual workload requirements. For instance, if your application demands a minimum of 2 ACUs but you've set the minimum to 0.5, the system will likely operate at 2 ACUs consistently to meet your workload needs. Therefore, carefully analyze your workload patterns and adjust your ACU settings accordingly to optimize performance and cost-efficiency.