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DOP-C02 Practice Question 14: Arc Routing Control Failover

AWS Certified DevOps Engineer – Professional (DOP-C02) · Test 2 · question 4 of 10

Resilient Cloud Solutionshard

A trading platform runs active-passive in two AWS Regions behind Amazon Route 53 failover records. After a past incident in which flapping health checks caused repeated automatic failovers, leadership set three requirements. Failover between Regions must be decided by operators, not by endpoint health checks. The failover procedure must not depend on the AWS Management Console, because consoles may be impaired during a Regional event. And a guardrail must stop anyone from accidentally switching both Regions off at the same time.

Which solution meets these requirements?

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Answer:

  • C. Create an Amazon Application Recovery Controller (ARC) cluster with one routing control per Region, attach routing control health checks to the failover records, add an assertion safety rule requiring at least one routing control to be On, and have operators call UpdateRoutingControlState through any of the five cluster endpoints

ARC routing controls are on/off switches built for operator-driven failover. Each routing control creates a routing control health check, and you associate that health check with the DNS failover record for a Region. Setting the control's state changes the health check, and Route 53 then shifts traffic. The decision belongs to the operator, so health-check flapping cannot trigger failover. A cluster is a data plane of five redundant Regional endpoints, and AWS's best practice is to use the data plane API (UpdateRoutingControlState, ListRoutingControls) through the AWS CLI or SDK rather than the console, trying another endpoint if one is unavailable. An *assertion* safety rule on the control panel, for example "at least one routing control is On", blocks an update that would leave no Region serving traffic. That is the fail-open guardrail the stem asks for.

Option A is exactly the behaviour leadership banned: health checks on endpoints make failover automatic, and a lower failure threshold makes flapping *more* likely, not less.

Option B makes the decision manual, but it has no guardrail. Nothing stops an operator from setting both weights to 0, which is the accident the stem describes. Record changes also go through the Route 53 API rather than a failover data plane designed for this job.

Option D has the right components and the right safety rule, but it breaks the second requirement. It relies on the console, which the ARC best practices specifically advise against for changing routing control states during an event.

References: Routing control components; Best practices for routing control in ARC

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