Service-Level Objective (SLO)

Outcome: Design or review Service-Level Objective (SLO) for this system while keeping data correct, secure, and easy to operate. User context: A checkout team measures requests that succeed within 300 ms. Its SLO is 99.9% over 28 days. Technical concept or control: Service-Level Objective (SLO). Why it fits: Use an SLO to choose reliability work with product owners. Name the user journey, signal, target, owner, and time window. Do not use it when: Do not call every metric an SLO. A target without an owner or decision rule is only a dashboard number. Engineering requirements: Define inputs, outputs, contracts, and rules that must always hold. Set authorization and input checks. Define failures, timeouts, retries, one-time effects, data moves, and compatibility limits. Operations: Add useful signals and logs that hide sensitive data. Set capacity limits and write an operator guide. Test recovery and rollback. Acceptance criteria: Contract and failure-path tests pass. Data and authorization rules still hold during retries and partial failures. Check performance limits, monitoring, recovery, and rollback. Evidence and limits (evidence boundary): No single official standard controls the whole term. Its meaning may change across teams, platforms, or frameworks. Unknowns to confirm: Where the code runs, data stores, traffic shape, consistency needs, and the security boundary. Also confirm the compatibility period, service goals, and rollback limits.