RDS workloads often evolve — changing engine types, rightsizing instances, or shifting to Aurora or serverless models. When these changes occur after Reserved Instances have been purchased, the existing commitments may no longer match active usage. This results in silent overspend, as underutilized RIs continue billing without offsetting usage.

Unlike Convertible EC2 RIs, RDS RIs cannot be exchanged. Selling unused RDS RIs is not supported. In rare cases, AWS Support may approve a goodwill adjustment, but this is not guaranteed. The most effective way to recover value is to steer eligible workloads back toward the reserved configuration.

Many RDS workloads continue to run on older x86 instance types (e.g., db.m5, db.r5) even though compatible Graviton-based options (e.g., db.m6g, db.r6g) are widely available. These newer families deliver improved performance per vCPU and lower hourly costs, yet are often not adopted due to legacy defaults, inertia, or lack of awareness.When workloads are not tightly bound to architecture-specific extensions (e.g., x86-specific binaries or drivers), switching to Graviton typically requires no application changes and results in immediate savings. Persisting with x86 in eligible use cases results in avoidable overpayment for compute.

While stopping an RDS instance reduces runtime cost, AWS enforces a 7-day limit on stopped state. After this period, the instance is automatically restarted and resumes incurring compute charges — even if the database is still not needed. This creates waste in cases where teams intended to pause the environment but failed to manage its lifecycle beyond the 7-day window. Without proper automation or teardown workflows, stopped RDS instances silently become active and billable again. The best practice for long-term inactivity is to snapshot the database and delete the instance entirely. If the instance must remain available for fast recovery, automation should be in place to re-stop it upon restart.

This inefficiency occurs when an RDS instance uses a high-cost storage type such as io1 or io2 but does not require the performance benefits it provides. In many cases, provisioned IOPS are set at or below the free baseline included with gp3 (3,000 IOPS and 125 MB/s). In such scenarios, continuing to use provisioned IOPS storage results in elevated cost with no functional advantage. These misconfigurations often persist due to legacy templates, default settings, or a lack of periodic review.

This inefficiency occurs when an RDS instance remains in the running state but is no longer actively serving application traffic. These instances may be remnants of retired applications, paused development environments, or workloads that were migrated elsewhere. If an instance shows no active connections and sustained inactivity across CPU and memory metrics, it is likely idle and generating unnecessary costs.

This inefficiency occurs when an RDS instance is consistently operating below its provisioned capacity—for example, showing low CPU, or memory utilization over an extended period. This often results from conservative initial sizing, decreased workload demand, or failure to review and adjust after deployment. Running oversized RDS instances leads to unnecessary compute and licensing costs without delivering additional value.

This inefficiency occurs when an RDS instance is allocated significantly more storage than it consumes. For example, a 2TB volume might contain only 150GB of actual data. Since RDS does not allow reducing allocated storage on existing instances, these volumes continue to incur charges based on total provisioned size—not actual usage. This often goes unnoticed in long-running databases that no longer require their original allocation.

When an RDS cluster is not upgraded in time, it can fall out of standard support and incur Extended Support charges. This often happens when upgrade cycles are delayed, blocked by compatibility issues, or deprioritized due to competing initiatives. Over time, these fees can add up significantly. Staying on an outdated version also increases operational risk and reduces access to engine improvements, performance enhancements, and security patches.

This inefficiency occurs when an RDS cluster remains provisioned but is no longer serving any workloads and has no active database connections. Unlike underutilized resources, these clusters are completely idle—showing no query activity, background processing, or usage over time. They often persist in dev, staging, or legacy environments where the workload has been retired or moved, yet the cluster remains active and continues to generate ongoing compute and storage costs.

Manual snapshots are often created for operational tasks like upgrades, migrations, or point-in-time backups. Unlike automated backups, which are automatically deleted after a set retention period, manual snapshots remain in place until explicitly deleted. Over time, this can lead to an accumulation of snapshots that are no longer needed but still incur monthly storage charges. This is particularly common in environments where snapshots are taken frequently but not consistently reviewed. If left unmanaged, manual snapshots can become a source of ongoing cost, especially for large databases or when snapshots are copied across regions.