Failure class
Name resolution or route withdrawal makes systems unreachable.
4 incidents on record
A single-site DNS outage degraded IDE code completions for 4% of Copilot users, delayed 25% of Actions workflows by over 5 minutes, and caused a complete code search outage for roughly 4 hours.
A quick mitigation for a localized infra failure can silently break cross-site connectivity elsewhere, so any DNS or routing fix should be validated for its effect on the broader topology before being treated as the resolution.
Facebook, Instagram, WhatsApp gone globally for ~6 hours. Internal tools, badge access and conference systems were down too, slowing recovery.
A safety mechanism reacting to a bigger failure can amplify it. Watch for circular dependencies where the tools to fix an outage are taken out by it.
EC2 instances in the AWS AP-NORTHEAST-2 (Seoul) region were unable to resolve DNS for 84 minutes, affecting all customers running workloads in that region.
Configuration parameters that control minimum capacity thresholds must have semantic validation — silently defaulting to zero when a floor setting is removed is a single config push away from a regional outage.
GitHub.com was fully unavailable for 42 minutes on January 8, 2014, with an additional 95 minutes of degraded access for a subset of repositories while fileservers were triaged and restored.
Deployment systems that regenerate critical infrastructure config (like DNS zone files) must validate API responses for completeness before applying them — and must never depend on the very service they are rebuilding.