Question

Your team runs a checkout API. A single user-facing 'complete purchase' journey involves three internal calls: cart validation, payment authorization, and order confirmation. Leadership set a 99.9% SLO for the overall purchase journey, but your current SLIs measure availability of each of the three backend services independently, and each individually reports around 99.9%. Users still complain that purchases frequently fail. What is the most appropriate SRE action to align your measurement with the user experience?

Accepted Answer

Define a journey-level SLI that measures the success rate of the end-to-end purchase request as experienced by the user, rather than relying only on per-service availability.

Answer

Raise each backend service's individual SLO target to 99.99% so the combined availability mathematically reaches 99.9%.

Answer

Average the three per-service SLIs together and report that mean as the journey SLI.

Answer

Add more replicas to each backend service until user complaints stop, then keep the existing per-service SLIs.