This following content is a transcript from Site Reliability Engineering with some, maybe none, personal adjustments.
Efficient use of resources is relevant any time a service cares about money. Because SRE ultimately controls provisioning, it must also be involved in any work on utilization, as utilization is a function of how a given service works and how it is provisioned. It follows that paying close attention to the provisioning strategy for a service, and therefore its utilization, provides a very, very big lever on the service’s total costs.
Resource use is a function of demand (load), capacity, and software efficiency. SREs predict demand, provision capacity, and can modify the software. These three factors are a large part (though not the entirety) of a service’s efficiency.
Sofware systems become slower as the load increases. A slowdown in a service equates to a loss of capacity. At some point, a slowing system stops serving, which corresponds to infinite slowness. SREs provision to meet a capacity target at a specific response speed, and thus are keenly interested in a service’s performance. SREs and product developers will (and should) monitor and modify a service to improve its performance, thus adding capacity and improving efficiency.