We dissected the official AWS US-East-1 post-mortem. If you rely on automated rollback or self-healing systems, this is a must-read. The true root cause of the last major AWS outage wasn't capacity—it was a latent defect in the automated DNS Enactor system.
The $581M Failure Breakdown 💥
The automation designed to ensure resilience turned into the primary vector of failure:
The Latent Defect: A slow "Enactor" process in one Availability Zone (AZ) caused its DNS update plan to be flagged as old.
The Critical Error: The automated cleanup system then deleted the "active" plan for dynamodb.us-east-1.amazonaws.com, resulting in zero IP addresses for the regional endpoint.
The Cascade: DynamoDB went dark. All dependent services (including EC2's internal controls and Load Balancer health checks) failed to replace faulty instances, compounding the problem.
The AWS team was ultimately forced to stop the automation to begin the recovery process manually.
The Core Architectural Flaw
The most critical takeaway is the design choice intended for resilience: For "resilience," the Enactors are not allowed to coordinate via a distributed locking service.
This decision, aimed at preventing a single global deadlock, ultimately created the specific condition for a total failure of the regional control plane.
What’s scarier: Vendor lock-in or automation gone rogue?
Read our full technical breakdown and the six architectural mandates we derived from this incident—including why Multi-AZ is no longer sufficient and how to build truly isolated Multi-Region systems.
👉 Full Technical Post-Mortem Analysis:
The AWS Outage Post-Mortem That Proves Everything You Know About Cloud Resilience Is Wrong | by Sohail Mohammed | Oct, 2025 | AWS in Plain English
October 19, 2025: AWS’s own DNS race condition killed DynamoDB for 14 hours. What they discovered challenges 10 years of “best practices.”
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