Reserved Instances and Azure Hybrid Benefit

Azure Reservations are one- or three-year commitments to specific Azure resource configurations in exchange for significant discounts compared to pay-as-you-go pricing. Reservations are paid upfront or monthly, and the discount is automatically applied to any matching resource you have running — you do not need to change anything about how you deploy the resources. Reservations are the primary cost optimisation tool for stable, predictable workloads.

Reserved VM Instances (RVIs) provide up to 72% savings over pay-as-you-go VM pricing. When you purchase an RVI, you specify the VM series (e.g., D-series v5), region (e.g., East US), and OS (Windows or Linux). Azure automatically applies the reservation discount to any running VM of that specification during the reservation term. You can choose instance size flexibility to allow the discount to apply across different sizes within the same VM family.

Reservations extend beyond VMs to cover many Azure services. Azure SQL Database Reserved Capacity provides up to 70% savings on provisioned vCore costs. Cosmos DB Reserved Throughput offers up to 65% savings on provisioned RU/s. Azure Synapse Analytics, Azure Cache for Redis, and Azure Blob Storage also have reservation options. Purchasing capacity reservations for databases often delivers the largest absolute dollar savings for data-heavy organisations.

When purchasing a reservation, you select its scope — which determines which subscriptions the discount applies to. Single subscription limits the discount to one subscription, useful for department-specific charge allocation. Single resource group limits to one resource group. Shared scope applies the discount across all subscriptions in your billing account or enrolment, maximising utilisation of the reservation across your entire fleet.

Azure provides flexibility to manage reservations after purchase. You can exchange a reservation for another of equal or higher value if your workload needs change (e.g., switching from D2s to D4s). You can cancel a reservation for a pro-rated refund subject to a 12% early termination fee (capped at $50,000 per year). The Reservations blade in the portal shows utilisation percentage, helping you identify under-used reservations to exchange or cancel.

Azure Hybrid Benefit (AHB) is a Microsoft licensing offer that lets organisations reuse existing on-premises Windows Server and SQL Server licences covered by Software Assurance (SA) on Azure resources. Instead of paying for the bundled OS/database licence component in the Azure VM price, you pay only for the base compute — a discount of 38% on Windows VMs and up to 85% on SQL Server when combined with a Reserved Instance.

Software Assurance (SA) is a Microsoft volume licensing programme that provides upgrade rights, technical support, and training benefits. Azure Hybrid Benefit requires that the licences you bring to Azure are covered by active SA or are subscription licences (e.g., part of Enterprise Agreement). You self-attest compliance with AHB terms; Microsoft performs periodic licence audits. Without active SA, applying the benefit is a licensing violation.

For SQL Server on Azure VMs (IaaS), AHB allows you to bring your own SQL Server Enterprise or Standard licences. A standard on-premises SQL Server Enterprise licence with SA covers up to 4 Azure VM vCores. If you also apply a Windows Server licence, you eliminate both OS and database licence charges, paying only for the base compute VM cost. The SQL IaaS Agent extension is recommended to manage AHB licensing from the Azure portal.

The maximum cost savings come from stacking Reserved Instances with Azure Hybrid Benefit. On a Windows SQL Server VM: PAYG list price might be $0.40/hour; applying a 3-year Reserved Instance brings it to $0.15/hour (62% saving); then applying AHB for Windows Server and SQL Server removes licence costs, bringing the total to potentially $0.05-0.08/hour — an overall saving of up to 85% compared to PAYG. This strategy is standard practice in enterprise Azure deployments.

Visual Studio subscribers receive additional benefits for non-production environments. Dev/Test pricing removes the Windows Server and SQL Server licence costs from VMs in Azure Dev/Test subscriptions, similar to Hybrid Benefit but applicable even without Software Assurance. Each Visual Studio subscriber is entitled to a fixed monthly Azure credit and access to Dev/Test images. Resources in Dev/Test subscriptions must not run production workloads.

An unused reservation still costs money, so monitoring reservation utilisation is essential. In Azure Cost Management, the Reservation Utilisation report shows the percentage of reserved capacity that was actually matched by running resources each day. Utilisation below 80% suggests the reservation is over-purchased and you should consider exchanging it for a smaller size. Azure Advisor also proactively alerts you when reservations are consistently underutilised.

Test your understanding of Microsoft Azure Fundamentals (AZ-900) concepts from this lesson.

In this lesson you learned: Reserved Instances provide up to 72% savings for stable workloads in exchange for 1- or 3-year commitments, Azure Hybrid Benefit reuses existing Windows Server and SQL Server SA licences to eliminate licence costs in Azure, and stacking reservations with AHB delivers up to 85% savings compared to pay-as-you-go pricing. Next up we explore Azure Governance with management groups and subscriptions.