Primary Trigger: A latent race condition in the DynamoDB DNS management system between two independent components: DNS Planner (monitors health, creates DNS plans) and DNS Enactor (applies plans to Route53). The system manages hundreds of thousands of DNS records across multiple endpoints including regional, FIPS, IPv6, and account-specific endpoints using a single shared regional plan for simplified capacity management.
Race Condition Mechanism: One DNS Enactor experienced unusual processing delays while working through endpoint updates. During this delay, a second Enactor completed applying a newer generation plan and triggered the cleanup process to delete older plans. The delayed Enactor then applied its stale plan to the regional endpoint (dynamodb.us-east-1.amazonaws.com), which was immediately deleted by the cleanup process, leaving an empty DNS record. The initial staleness check had become invalid due to the processing delays, allowing the outdated plan to be applied.
Cascading Failure Chain: Empty DNS record → All new DynamoDB connections failed → EC2 DWFM lost state check capability → Droplet leases timed out → EC2 launches failed → DWFM congestive collapse → Network Manager backlog → NLB health check oscillations → Lambda, ECS/EKS/Fargate, Connect, STS, Redshift, IAM, and Support Center failures.
Recovery Challenge: The empty DNS state was inconsistent and prevented automatic recovery mechanisms from functioning, requiring manual operator intervention at 2:25 AM EST to restore DNS information.
Complete service outage from 2:48 AM to 5:40 AM EST (2 hours 52 minutes). DNS endpoint became unresolvable, blocking all new connections.
Direct Dependencies:
Cascading Impacts:
Component: DNS Enactor race condition
Trigger: One DNS Enactor experienced unusual delays processing endpoints. While delayed, another Enactor completed a newer plan and triggered cleanup of older plans. The delayed Enactor then applied its stale plan to the regional endpoint, which was immediately deleted by cleanup.
Failure Mode: Empty DNS record left the system in an inconsistent state that prevented automatic recovery.
New instance launches failed for 5 hours 40 minutes, followed by 5 hours 55 minutes of network connectivity issues.
Depends On:
Cascading Impacts:
Customers received: InsufficientCapacity and RequestLimitExceeded
Launches succeeded but instances had no network connectivity
Gradual throttle relaxation, occasional RequestLimitExceeded
DWFM Congestive Collapse: DropletWorkflow Manager queued work to re-establish droplet leases faster than it could complete them. Work timed out and was re-queued, creating a feedback loop.
Network Manager Backlog: Large backlog of delayed network state changes (accumulated during DWFM failure) overwhelmed Network Manager, causing propagation delays of 2-3 hours.
Function creation/updates failed. SQS/Kinesis processing stopped. Internal systems under-scaled due to NLB failures.
Impacts:
Health check oscillations caused connection errors for some load balancers.
Impacts:
Health check subsystem brought new EC2 instances into service before Network Manager propagated network state. Health checks alternated pass/fail, causing nodes to be repeatedly removed and added.
Container launch failures and cluster scaling delays across all three services from 2:45 AM to 5:20 PM EST (14 hours 35 minutes).
Depends On:
Services Affected:
Primary Dependency: All three services rely on EC2 for underlying compute capacity.
Failure Chain: DynamoDB outage → EC2 DWFM failure → No new instances → Container launch failures
Impact Duration: Services remained impaired throughout the entire EC2 recovery period including the degraded and recovering phases.
Two distinct impact periods: initial DynamoDB-related failures, then NLB/Lambda-related errors.
Depends On:
Customer-Facing Impacts:
Two brief impact periods: initial DynamoDB dependency, then NLB health check failures.
Service Function:
STS provides temporary security credentials for AWS services and federated users.
Initial query processing failures, followed by prolonged cluster unavailability due to EC2 dependency.
Depends On:
Query processing failed due to inability to read/write DynamoDB metadata
Clusters stuck in "modifying" state as credential refresh triggered replacement workflows that couldn't complete due to EC2 launch failures
IAM user credential queries failed globally due to Redshift calling IAM APIs in us-east-1
Multiple Failure Modes:
1. Query Processing: Redshift uses DynamoDB to read/write cluster metadata. DynamoDB outage blocked all query operations.
2. Credential Refresh Loop: As node credentials expired, Redshift automation triggered EC2 instance replacements. EC2 launch failures caused workflows to stall, leaving clusters in "modifying" state.
3. Cross-Region Defect: Redshift hardcoded IAM API calls to us-east-1 for user group resolution, causing global IAM user authentication failures.
Console authentication failures for IAM users and Identity Center in us-east-1.
Affected User Types:
Support case creation, viewing, and updates blocked despite successful failover to backup region.
Components:
Failover Status:
✓ Regional failover successful
✗ Metadata subsystem returned invalid responses
Design Flaw: Account metadata subsystem had three possible response states:
1. ✓ Valid response (access granted)
2. ✓ Error response (bypass enabled)
3. ✗ Invalid response (incorrectly blocked)
Failure: During the incident, the subsystem returned invalid responses instead of error responses, which prevented the bypass logic from activating.