RDS Proxy | RDS/Aurora cost optimization

Why it matters

RDS Proxy sits between your application and your RDS or Aurora database, managing connection pooling intelligently so your app doesn’t waste compute resources opening and closing database connections repeatedly. For serverless applications (Lambda), microservices, and other workloads with variable or unpredictable connection patterns, RDS Proxy can reduce database CPU load, improve failover behavior, and allow you to handle more application scale without necessarily increasing database instance size.¹

How RDS Proxy helps with costs

Reduces database compute pressure – Connection pooling means fewer active connections and lower CPU/memory overhead on the database instance, which can delay or eliminate the need to scale up to a larger (more expensive) instance class.
Enables efficient serverless patterns – Lambda functions and other ephemeral compute can create connection storms; RDS Proxy reuses connections so you avoid paying for excess database capacity just to handle connection churn.
Improves failover time – Faster failover (up to 66% reduction in recovery time) means less downtime and fewer lost transactions, which has indirect cost benefits for availability-sensitive workloads.²

When RDS Proxy makes sense

RDS Proxy is most valuable when:

Serverless or autoscaling compute – Lambda functions, ECS/EKS with horizontal pod autoscaling, or any workload where the number of application instances changes rapidly and unpredictably.
Connection storms – Applications that open many short-lived connections (for example, microservices, batch jobs, ETL pipelines) rather than maintaining long-lived connection pools.
High availability requirements – Workloads where reducing failover time is critical and where automatic rerouting to read replicas during failures is valuable.
Credential management – Teams that want to centralize database credentials in AWS Secrets Manager and rotate them without application changes.¹

When RDS Proxy may not help

Avoid or deprioritize RDS Proxy when:

Stable, long-lived connections – Traditional applications with persistent connection pools (for example, application servers with fixed pool sizes) already manage connections efficiently and may not benefit from an additional proxy layer.
Very low connection counts – Workloads with only a handful of concurrent connections won’t see meaningful compute savings.
Cost sensitivity on small workloads – RDS Proxy is billed per vCPU-hour of the proxy fleet; for small, low-traffic databases, the proxy cost may outweigh the savings from reduced database compute.³
Custom Aurora endpoints – RDS Proxy does not route through custom Aurora endpoints (for example, custom reader endpoints or instance-specific endpoints). If your application relies on custom endpoints for specific routing logic, connection handling, or workload isolation, you cannot use RDS Proxy for those connections—the proxy only connects to the cluster’s default endpoints.

Implementation considerations

Connection pooling and load balancing
- RDS Proxy maintains a pool of connections to your database and reuses them across application requests, reducing the overhead of connection establishment.
- For Aurora clusters with read replicas, configure RDS Proxy to route read traffic across replicas to distribute load more evenly than application-side routing often achieves.
Automatic failover
- In a Multi-AZ or Aurora cluster configuration, RDS Proxy can detect database failures and reroute connections to a standby or read replica without the application needing to handle reconnection logic.
- AWS documentation states this can reduce failover time by up to 66% compared to applications managing failover themselves.²
Secrets Manager integration
- RDS Proxy integrates with AWS Secrets Manager to retrieve database credentials, so you can rotate passwords without updating application configuration or restarting services.
Network security
- Place RDS Proxy in the same VPC as your database and application tier.
- Use security groups to ensure only the proxy can reach the database, and only approved application services can reach the proxy, creating a clear network boundary.
Framework compatibility
- Most database client libraries and frameworks (for example, SQLAlchemy, Django ORM, JDBC) work transparently with RDS Proxy; you simply point the connection string at the proxy endpoint instead of the database endpoint.
- For read/write split workloads, confirm your framework or application logic can route queries to the appropriate proxy endpoint (read-only vs. read-write).

Cost structure

RDS Proxy is billed based on the number of vCPUs in the proxy fleet and the hours it runs.³ The proxy fleet size is determined by AWS based on your workload’s connection and throughput requirements, so costs scale with usage.

For small databases, the incremental proxy cost may be noticeable; for larger workloads where connection management is a bottleneck, the proxy cost is typically offset by the ability to avoid upsizing the database instance or reducing CPU/memory pressure on the existing instance.

Practical approach

Identify high-connection-churn workloads
- Look for Lambda-backed APIs, microservices with high request variability, or ETL jobs that create many concurrent connections.
- Check CloudWatch metrics for DatabaseConnections on your RDS/Aurora instances; if connections spike frequently or are high relative to instance capacity, RDS Proxy may help.
Start with non-production or lower-risk workloads
- Create an RDS Proxy for a staging or dev environment first to validate behavior and measure connection and CPU changes before rolling out to production.
Measure before/after
- Compare database CPU utilization, connection counts, and application latency before and after introducing RDS Proxy to confirm the expected improvements and justify the proxy cost.
Combine with application-level improvements
- RDS Proxy is most effective when paired with sensible application-side connection practices (for example, reasonable connection timeouts, retry logic with exponential backoff and jitter).
- Don’t rely on RDS Proxy alone to solve poorly designed connection handling in your application code.