Toil is work tied to running a production service that is manual, repetitive, automatable, tactical, devoid of enduring value, and scales linearly with service growth. Not all operational work is toil. Capacity planning requires judgment. Postmortem analysis produces lasting improvements. Writing automation code is engineering. Toil is the opposite: it is the work that a machine could do but currently a human is doing, over and over, without making the system any better.
February 22, 2026
Site Reliability Engineering treats operations as a software engineering problem. Instead of a wall between developers who ship features and operators who keep things running, SRE defines reliability as a feature – one that can be measured, budgeted, and traded against velocity. The core insight is that 100% reliability is the wrong target. Users cannot tell the difference between 99.99% and 100%, but the engineering cost to close that gap is enormous. SRE makes this tradeoff explicit through service level objectives.