Cases2 cases

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1. IL-0366 Cloud Storage uploads and writes in us-central1 slowed and failed with HTTP 503 as traffic piled onto a few backends

   Google Cloud2026

   Symptoms

   From 04:00 US/Pacific on 8 October 2026, Google Cloud Storage upload and write operations in the us-central1 region became slow and failed. Clients mostly saw HTTP 503 UNAVAILABLE errors on WriteObject operations and client-side timeouts.

   High latencyHigh error rateLoad imbalance

   Trigger

   A configuration update to the Cloud Storage load balancing layer turned on a traffic sorting optimization that was meant to deal with local capacity constraints. The recurrence on 9 October came from an incomplete rollback of an upload planner feature.

   Root cause

   Configuration change

   Component

   Object storageDatabase

   Contributing factor

   No headroomOverlapping failures

   Detection

   Google engineering teams monitoring system telemetry detected the problem at 04:50 US/Pacific on 8 October, 50 minutes after it began.

   Remediation

   • Drained traffic from the most overloaded storage backend nodes
   • Deployed a configuration change that disabled the traffic sorting optimization
   • Rolled back a recent update to the metadata database service
   • Redirected traffic and drained affected storage components again during the recurrence
   • Fully reverted the load balancing configuration change, restoring capacity-aware routing
   • Returned the drained nodes to service once resource use was back to normal

   Action items

   • Validate load balancing logic changes in smaller regions before rolling them out to large, highly utilized regions
   • Make the storage load balancing enforce capacity constraints so traffic cannot bypass pre-spilling safeguards
   • Speed up internal data movement within highly utilized storage cells to absorb temporary load spikes

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2. 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 CDN

   bunny.net2021

   Symptoms

   On 22 June 2021, within minutes of an update released at 8:25 AM UTC, bunny.net's global fleet of close to 100 DNS servers kept crashing and restarting, more than 60% of traffic was lost, hundreds of Gbits of throughput disappeared, and over 750,000 websites were affected. After 10 minutes the team realised that the DNS servers were restarting and dying and that nothing could bring them back up in that state.

   Container crash loopDNS resolution failuresService outageMisrouted requestsLoad imbalance

   Trigger

   At 8:25 AM UTC bunny.net released an update meant to reduce the download size of the SmartEdge optimization database, and it uploaded a corrupted file to Edge Storage.

   Root cause

   Faulty deployment

   Component

   Authoritative DNS servers and recordsCDN and edge networkObject storage

   Contributing factor

   Circular dependencySingle point of failureAutomation amplificationIneffective rollbackHarmful manual action

   Detection

   About 10 minutes after the release, the team realised that the DNS servers were restarting and dying.

   Remediation

   • Deployed by hand an update that disabled the SmartEdge system on the DNS nodes
   • Routed all requests through Frankfurt instead of Madrid on a couple of DNS servers
   • Migrated the deployment systems and files to a third-party cloud storage service
   • Rewired the deployment system and DNS software to the new storage and deployed
   • Synced the databases and deployed the newest file sets through the third-party service

   Action items

   • Phase out the BinaryPack library as a hot-fix
   • Test third-party libraries more extensively
   • Migrate the internal APIs to an independent third-party service
   • Find how to stop non-critical software from becoming a single point of failure across clusters
   • Make the DNS system keep a local copy of all backup data with automatic failure detection

   Lessons

   bunny.net had built its systems to rely on each other, including the critical parts of its internal infrastructure, so one corrupted file brought down several layers of redundancy with no way back. A part of the infrastructure treated as non-critical turned out to be a single point of failure for several clusters at once, which canary deployments did not catch. Building infrastructure inside its own ecosystem lets one failure cascade through all of it. In the rush to fix the outage the team made typos and mistakes, and the final deployment came after it calmed down and double-checked everything.

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