For many customers, seeing their Microsoft costs escalate dramatically (doubling and even tripling) is a sobering moment. But in all fairness, the Microsoft licensing model has changed to reflect a more modern approach to consumption - and they're not the only big vendor in the market to do so. Microsoft's new service agreement and metrics are a way to ensure that their paying customers receive the best possible service and platform deliverability.
How does that work, exactly? Let's say Customer A in a multi-tenancy infrastructure has low API usage to the backend of their Microsoft solution. But their neighbour, Customer B, is an extremely heavy user of APIs. The bad news is that Busy B can impact the performance of the tenancy for Average-user A and everyone else, especially when this consumption is a “surprise” or unexpected by Microsoft, as this spike impacts the ability of the data centre to perform at its optimum.
Microsoft's introduction of the SLA and metrics mechanism ensures uptime quality of service and performance - and provide some fairness. Those customers with low API workloads won't have their performance impacted by those with heavy integration workloads. And those who do have significant workloads will have to pay for their overt consumption.
That's all well and good. But when you go from never having your API workload measured, to paying by call, it can add a considerable financial burden - which although mitigated by the brilliant platform you have access to – can be a huge shock.