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SESK: Stuff Everyone Should Know · sesk.info/tech-failover-healthy-resource

What must happen during a successful failover?

Requests shift to a healthy resource that can continue service.

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  1. Every log is deleted
  2. The failed resource stays primary
  3. A healthy resource takes over ✔

Why: Redundancy supplies the spare capacity, but failover activates or routes to it. Health detection and traffic switching are therefore part of the design.

Huh, didn't know that: A database replica may need promotion before it can accept primary writes.

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The standby server heard its cue and stepped into the spotlight.
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References

Answer: A healthy resource takes over. Redundancy supplies the spare capacity, but failover activates or routes to it. Health detection and traffic switching are therefore part of the design.

  1. AWS Well-Architected Fail Over to Healthy Resources docs.aws.amazon.com/wellarchitected/2022-03-31/framework/rel_withstand_component_failures_failover2good.html
    Ensure that if a resource failure occurs, that healthy resources can continue to serve requests.
    Checked 2026-10-10.

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