Incident Library
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  1. IL-0341 Traffic between Cloudflare and AWS us-east-1 had high latency, packet loss and origin failures for almost four hours
    Cloudflare2025
    Symptoms

    From 16:27 UTC on 21 August 2025, users connecting to Cloudflare from servers in AWS us-east-1, or receiving connections from Cloudflare there, saw high latency, packet loss and failures to reach origins. Cloudflare's network team was alerted to internal congestion in Ashburn (IAD) at 16:44 UTC.

    Packet lossHigh latencyIntermittent timeouts
    Trigger

    At about 16:27 UTC a single customer began sending many requests from AWS us-east-1 to Cloudflare for objects in Cloudflare's cache, doubling the total traffic from Cloudflare to AWS.

    Root cause
    Capacity exhaustion
    Component
    Transit gateway or network interconnectBGP routingCDN and edge network
    Contributing factor
    No headroomHarmful manual actionExcessive blast radius
    Detection

    Cloudflare's network team was alerted to internal congestion in Ashburn (IAD) at 16:44 UTC, and an incident was raised for customer impact at 17:45 UTC.

    Remediation
    • Rate limited the single customer whose traffic caused the surge
    • Took further traffic engineering actions that fully resolved the congestion
    • Asked AWS to revert its BGP prefix withdrawals, which AWS finished at 20:07 UTC
    Action items
    • Build a mechanism to deprioritise a customer's traffic when it congests the network enough to affect others
    • Speed up the Data Center Interconnect upgrades to add network capacity
    • Work with AWS so the two companies' BGP traffic engineering actions do not conflict
    • Build a traffic management system that gives each customer a network resource budget and automates the manual actions used here
    Lessons

    Cloudflare concludes that it must isolate customers better so that no single customer can take over shared network resources and degrade the platform for others, and that its network needs enough capacity to meet demand. It describes the outage as the result of insufficient network congestion management during an unusual high-traffic event.

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This case involves BGP routing and CDN and edge network. kubegap audits a Kubernetes cluster for gaps like these, read-only, from Claude Code or Codex; its checks cite public reports like the ones in this library.

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By root cause1

Capacity exhaustion1 case

Component
BGP routingCDN and edge networkTransit gateway or network interconnect
Contributing factor
Excessive blast radiusHarmful manual actionNo headroom
Organisation
Cloudflare
  1. IL-0341 Traffic between Cloudflare and AWS us-east-1 had high latency, packet loss and origin failures for almost four hours
    Cloudflare2025