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From October 19th to October 20th, 2025, Amazon Web Services (AWS) experienced a significant outage, primarily in its US-EAST-1 Region.
Amazon Web Services is a collection of public cloud computing services that together form a cloud computing platform, offered via the Internet by Amazon.com. It is used in popular applications such as Dropbox, Foursquare, and HootSuite.
This outage began at approximately 11:48 PM PDT on October 19th and lasted for approximately 15 hours until the evening of October 20th.
This event disrupted a wide range of AWS services and had cascading effects on thousands of customer applications worldwide, given US-EAST-1’s role as a critical control plane for global operations.
AWS attributed the incident to “faulty automation” related to a latent race condition in its internal systems.
Amazon’s Explanation of the Automation Error
In its official post-incident summary, AWS detailed that the root cause was a rare race condition in DynamoDB’s automated DNS management system.
Two independent components, known as DNS Enactors, are responsible for managing DNS configuration plans across Availability Zones.
A latent flaw caused a temporary overlap; late processing of an older plan by one Enactor coincided with rapid cleanup of a newer plan by another Enactor.
This caused the old plan to overwrite the new one, thereby deleting all IP addresses associated with the DynamoDB regional endpoint (dynamodb.us-east-1.amazonaws.com).
The system entered an inconsistent state that prevented self-healing, resulting in high error rates in DNS resolution for DynamoDB APIs.
AWS emphasized that this was an isolated flaw in the automation logic, not a hardware failure or external attack, and that it was triggered by a unique sequence of events that had not been evident in previous testing.
The outage also caused broader internet disruptions, crashing major platforms such as Perplexity, Signal, and Coinbase, and affecting more than 1,000 websites globally due to their reliance on AWS infrastructure.
The incident exposed vulnerabilities stemming from over-reliance on a single region such as US-EAST-1, prolonging downtime for businesses worldwide.
Customers experienced connection failures, processing delays, and service unavailability, halting critical workflows such as e-commerce transactions, real-time data synchronization, and customer service operations (e.g., dropped calls on Amazon Connect).
While exact figures are not public, similar AWS outages in the past have cost affected businesses millions of dollars in lost revenue; the 15-hour duration of this event likely exacerbated the financial impact on high-traffic applications.
AWS faced public scrutiny and apologies to customers, highlighting ongoing concerns about the cloud provider’s reliability. The risks of automation-induced failures in complex, distributed systems were highlighted.
Global services experienced impact issues, with data replication delays extending beyond the initial resolution of the outage, potentially raising compliance issues for regulated industries.
No widespread data breaches or security incidents were reported, but the event prompted debate about cloud provider diversification and the implementation of multi-region architectures.
AWS concluded that the outage was due to insufficient safeguards against rare race conditions in automated systems, emphasizing the need for more robust testing in extreme scenarios on high-risk infrastructure. In its response, AWS outlined immediate and long-term mitigation measures:
Faulty DNS automation components were disabled and safeguards were implemented to prevent outdated plans from overwriting new ones, restoring services by the afternoon of October 20.
Preventative Measures:
Internal-scale testing for EC2 DWFM recovery workflows was expanded. Improved throttling mechanisms were implemented to manage load spikes on affected systems.
“Rate controls” were introduced in NLB to limit rapid capacity losses during failovers.
AWS reiterated its focus on infrastructure resiliency, recognizing the role of the outage as a “wake-up call” for the cloud ecosystem. Customers are encouraged to adopt multi-region deployments, automated failovers, and periodic chaos engineering to mitigate similar risks.
Overall, the incident reinforces the idea that while automation drives efficiency, it must be accompanied by rigorous validation to avoid single points of failure in mission-critical environments. AWS’s transparent post-analysis is seen as a positive step toward accountability, although it could lead to regulatory scrutiny over cloud outage reporting.
