A team argues that deploying a service in two zones guarantees near-perfect availability because the two instances are independent. What is the main flaw in this reasoning according to the SRE Workbook?

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B. Availability math is deceptive when systems share dependencies, control planes, or failure domains. The SRE Workbook warns that simple independence math is often deceptive because supposedly separate instances usually share dependencies, control planes, and other common failure domains. The issue isn't lack of monitoring support; it's the invalid assumption of true independence.

A team argues that deploying a service in two zones guarantees near-perfect availability because the two instances are independent. What is the main flaw in this reasoning according to the SRE Workbook?

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