Explanation
As workloads evolve, Azure Reserved Instances (RIs) may no longer align with actual usage - due to refactoring, region changes, autoscaling, or instance-type drift. When this happens, the committed usage goes unused, while new workloads run on non-covered SKUs, resulting in both underutilized reservations and full-price on-demand charges elsewhere.
The root inefficiency is architectural or operational drift away from what was originally committed - often due to team autonomy, poor RI governance, or legacy commitments. This leads to silent waste unless workloads are re-aligned to match existing reservations.
Relevant Billing Model
- Azure Reservations are prepaid or monthly-commit financial instruments
- The discount applies only when running matching resources (e.g., same VM size and region)
- Underutilized reservations result in sunk cost with no usage offset
- Azure offers limited flexibility via instance size flexibility, re-scoping, or exchange options
Detection
- Identify Azure Reservations with consistently low utilization rates
- Determine which SKUs, regions, or resource types are covered but underused
- Compare current usage patterns to reservation scope (e.g., VM series, region, size)
- Assess whether workloads moved off the committed types due to organic evolution, performance needs, or misaligned provisioning
Remediation
- Evaluate whether any existing workloads could be migrated to match the reservation scope
- For new workloads, consider provisioning on RI-covered instance types when technically viable
- Where appropriate, exchange the reservation for a more relevant SKU
- Re-scope the reservation to another subscription or region if cross-team usage can improve coverage
- Use RI utilization data to inform future purchasing decisions and reduce overcommit risk