Commercial and channel
Reserved Instances
Azure Reservations
An Azure reservation, also called a reserved instance, is a one-year or three-year commitment purchase that discounts the billing rate for a specific, matching configuration, such as a particular virtual machine size family in a particular Azure region, in exchange for that upfront commitment.
Why Reserved Instances matters in a Microsoft estate
Reserved Instances matters because Microsoft estate decisions often have a commercial owner as well as a technical owner. Clear cost, licence, and partner language helps teams prove value, reclaim waste, and agree the next action before spend becomes harder to challenge.
How Reserved Instances shows up in practice
Reservations are a billing construct rather than a change to how a resource runs: the workload behaves identically, only the price applied to matching usage changes. Three mechanics decide how well a reservation performs in practice. Scope determines how widely the discount can apply, from a single subscription up to a shared scope across an entire billing context. A shared scope is generally the most forgiving choice, because the discount searches for any matching resource across the estate rather than sitting unused if one subscription stops consuming it.
Instance size flexibility means a reservation for virtual machines can cover other sizes within the same flexibility group, not only the exact size purchased, using a ratio Azure applies internally, though it does not cross between different VM families. Exchange and refund policy governs what happens if the underlying need changes. This policy has been revised by Microsoft more than once, most recently tightening the window in which a reservation purchased for one configuration can be exchanged for another. The current terms should always be checked at the point of purchase, rather than assumed from memory.
The core risk with any reservation is the same regardless of these mechanics: it only pays off if the matching resource keeps running for the length of the term. A reservation bought for a virtual machine that is later resized, moved, or decommissioned becomes a sunk commitment rather than a saving. For that reason, reservations suit steady, well-understood workloads with no expected change in size or region, such as an always-on database tier or a line-of-business application that has held its shape for a year. They should always be purchased after rightsizing, not before, so the commitment reflects the workload the estate actually needs rather than the oversized footprint it started with.