Circular dependency

Cases

1. IL-0497 Buttondown's database ran out of connections twice in one day and requests failed while health checks mostly passedButtondown · 2026

   Root cause Capacity exhaustion

2. IL-0559 PubNub services degraded in US-East during an AWS outage in the IAD region, and failover load then degraded US-WestPubNub · 2025

   Root cause Cloud provider outage

3. IL-0284 Workers KV failed 90.22% of requests in a third-party storage outage, breaking Access, WARP and many Cloudflare productsCloudflare · 2025

   Root cause Cloud provider outage

4. IL-0227 Most Heroku dynos in Private Spaces lost outbound connectivity after an automated OS update restarted host networkingHeroku · 2025

   Root cause Breaking change in an upgrade

5. IL-0543 Twingate API traffic piled onto one backend behind the global load balancer, failing core services for 29 minutesTwingate · 2025

   Root cause Configuration change

6. IL-0285 Clever Cloud's Pulsar brokers stalled in a minor upgrade, then hypervisors overloaded and crashed with kernel panicsClever Cloud · 2024

   Root cause Configuration change

7. IL-0254 Square's internal DNS servers failed and Square products, services and payments were unavailable for about 15 hoursSquare · 2023

   Root cause Configuration change

8. IL-0223 A connection surge congested the devices between AWS's internal and main networks in us-east-1, breaking EC2 APIsAmazon Web Services · 2021

   Root cause Software defect

9. IL-0221 A backbone maintenance command disconnected all Facebook data centers, and its DNS servers withdrew their BGP routesMeta · 2021

   Root cause Operator error

10. IL-0229 bunny.net's DNS servers crashed in a loop on a corrupted routing database file and could not fetch a fix from its CDNbunny.net · 2021

    Root cause Faulty deployment

11. IL-0220 An overloaded AWS Transit Gateway dropped packets on 4 January 2021, and Slack's web tier saturated and went downSlack · 2021

    Root cause Cloud provider outage

12. IL-0384 Amazon Kinesis front-end servers in US-EAST-1 could not route requests, so Kinesis and services built on it failedAmazon Web Services · 2020

    Root cause Capacity exhaustion

13. IL-0272 New Cassandra nodes served reads for data they did not hold, so Monzo records looked missing and payments failedMonzo · 2019

    Root cause Configuration change

14. IL-0222 Google Cloud US regions had heavy packet loss and some went unreachable after the network control plane was descheduledGoogle Cloud · 2019

    Root cause Software defect

15. IL-0492 Hosted Graphite's self-hosted load balancers hit their connection limit in an AWS outage, timing out its site and APIsHosted Graphite · 2018

    Root cause Capacity exhaustion

16. IL-0534 Amazon S3 in US-EAST-1 could not serve GET, LIST, PUT or DELETE requests for hours while its index subsystem restartedAmazon Web Services · 2017

    Root cause Operator error

17. IL-0333 A downsized RDS PostgreSQL database maxed out its CPU at US peak and failing ELB health checks took buildkite.com downBuildkite · 2016

    Root cause Capacity exhaustion

18. IL-0273 A power disruption took GitHub's Redis clusters offline, the app could not boot, and GitHub served 503s for 2 hoursGitHub · 2016

    Root cause Dependency failure

19. IL-0282 DynamoDB in US-East reached about 55% request errors as storage servers overloaded its metadata serviceAmazon Web Services · 2015

    Root cause Capacity exhaustion