# Google Cloud Storage (GCS) customers experienced elevated latencies and error rates when performing upload or write operations.

- Provider: [Google Cloud](https://down.guide/gcp)
- Level: confirmed
- Impact: Partial outage
- lasted 1d 5h
- started 2026-10-08 11:00 UTC
- Google Cloud Storage
- us-central1
- id: DWN-ff8ca4e51a
- Official page: https://status.cloud.google.com/incidents/mSFVt6PiP557bjRyYsut

## Root cause
> We are working to address the root cause and prevent this from occurring in the future.

[Postmortem](https://status.cloud.google.com/incidents/mSFVt6PiP557bjRyYsut)

## Updates from Google Cloud
### 2026-10-08 18:24 UTC: service\_disruption
\*\*Summary\*\*
Google Cloud Storage customers are experiencing elevated latencies and error rates when performing upload or write operations
\*\*Description\*\*
We are experiencing an issue with Google Cloud Storage beginning on Thursday, 2026-10-08 05:19 PDT.
Our engineering team continues to investigate the issue.
We will provide an update by Thursday, 2026-10-08 11:50 PDT with current details.
\*\*Customer Symptoms\*\*
\* Customers are experiencing elevated latencies and error rates when performing upload or write operations.
\* A smaller subset of read operations may also experience increased latency and errors
\*\*Workaround\*\*
None at this time.

### 2026-10-08 18:34 UTC: service\_disruption
\*\*Summary\*\*
Google Cloud Storage customers are experiencing elevated latencies and error rates when performing upload or write operations
\*\*Description\*\*
We are experiencing an issue with Google Cloud Storage beginning on Thursday, 2026-10-08 05:19 PDT.
Initial mitigations applied by our engineering team leading to observable improvements in error rates in our internal monitoring. Work remains underway to roll out further mitigations.
We will provide an update by Thursday, 2026-10-08 12:00 PDT with current details.
\*\*Customer Symptoms\*\*
\* Customers are experiencing elevated latencies and error rates when performing upload or write operations.
\* A smaller subset of read operations may also experience increased latency and errors
\*\*Workaround\*\*
None at this time.

### 2026-10-08 18:55 UTC: service\_disruption
\*\*Summary\*\*
Google Cloud Storage customers are experiencing elevated latencies and error rates when performing upload or write operations
\*\*Description\*\*
We are experiencing an issue with Google Cloud Storage beginning on Thursday, 2026-10-08 05:19 PDT.
Initial mitigations applied by our engineering team leading to observable improvements in error rates in our internal monitoring beginning 10:57 PDT. Work remains underway to roll out further mitigations.
We will provide an update by Thursday, 2026-10-08 12:45 PDT with current details.
\*\*Customer Symptoms\*\*
\* Customers are experiencing elevated latencies and error rates when performing upload or write operations.
\* A smaller subset of read operations may also experience increased latency and errors
\*\*Workaround\*\*
None at this time.

### 2026-10-08 19:38 UTC: service\_disruption
\*\*Summary\*\*
Google Cloud Storage customers are experiencing elevated latencies and error rates when performing upload or write operations
\*\*Description\*\*
We are continuing to mitigate the issue with Google Cloud Storage in the us-central1 region that began on Thursday, 2026-10-08 05:19 PDT.
The initial mitigations applied by our engineering team continue to show observable improvements in error rates. Our engineering team is actively monitoring the environment and rolling out further mitigations to fully stabilize the service.
We will provide an update by Thursday, 2026-10-08 14:00 PDT with current details.
\*\*Customer Symptoms\*\*
\* Customers are experiencing elevated latencies and error rates when performing upload or write operations.
\* A smaller subset of read operations may also experience increased latency and errors
\*\*Workaround\*\*
None at this time.

### 2026-10-08 20:48 UTC: service\_disruption
\*\*Summary\*\*
Google Cloud Storage customers are experiencing elevated latencies and error rates when performing upload or write operations
\*\*Description\*\*
We are continuing to mitigate the issue with Google Cloud Storage in the us-central1 region that began on Thursday, 2026-10-08 05:19 PDT.
The initial mitigations applied by our engineering team continue to show observable improvements in error rates.
Our engineering team is actively monitoring the environment and rolling out further mitigations to fully stabilize the service.
We will provide an update by Thursday, 2026-10-08 16:00 PDT with current details.
\*\*Customer Symptoms\*\*
\* Customers are experiencing elevated latencies and error rates when performing upload or write operations.
\* A smaller subset of read operations may also experience increased latency and errors
\*\*Workaround\*\*
None at this time.

### 2026-10-09 16:44 UTC: resolved
## Preliminary Incident Report
We sincerely apologize for the disruption this incident caused to your business. We know how much you rely on Google Cloud, and we regret the impact on your productivity. We are working to address the root cause and prevent this from occurring in the future.
Please note, this information is based on our best knowledge at the time of posting and is subject to change as our investigation continues. A final Incident Report with preventative actions will be posted once our investigation is complete.
If you have experienced impact outside of what is listed below, please reach out to Google Cloud Support using \[https\\://cloud.google.com/support\](https://cloud.google.com/support)
## Date/Time of the Issue (All time US/Pacific)
Incident Start: 08 October 2026 04:00
Incident End: 08 October 2026 16:30
Duration: 12 hours, 30 minutes
## Summary
On Thursday, 08 October 2026, Google Cloud Storage experienced elevated write latency and write error rates in the us-central1 region for a duration of 12 hours, 30 minutes. We are taking immediate steps to ensure this doesn’t happen again.
## Preliminary Root Cause
Google Cloud Storage relies on a highly distributed backend architecture to process and store incoming data. During the incident window, specific storage backend nodes within the us-central1 region experienced a localized capacity shortfall.
The sequence of events leading to customer impact was as follows:
\* A traffic sorting optimization intended to address localized capacity constraints caused severe resource exhaustion on specific backend storage nodes in the affected region.
\* This resource exhaustion caused backend services handling object data ingestion to begin timing out.
\* As a result, incoming upload and write requests routed to these nodes experienced elevated latency and failed to complete, resulting in errors surfaced to customers.
\* Concurrently, a separate issue with the underlying database service contributed to additional metadata processing errors during a portion of the incident window.
Google engineers have begun a full root cause analysis (RCA) and will provide additional information once it is available.
## Remediation
The issue was initially detected by Google engineering teams actively monitoring system telemetry early in the incident window.
To mitigate the issue, Google engineers executed the following step-by-step strategy:
\* Engineers initially attempted to dynamically allocate additional emergency capacity to the affected region, but this was blocked by systemic regional capacity limits.
\* To relieve immediate pressure, engineers selectively drained traffic from the most overloaded backend storage nodes.
\* A configuration change was deployed to disable the traffic sorting optimization, significantly reducing resource overhead on the storage backend.
\* For the concurrent metadata issue, engineers rolled back a recent update to the underlying metadata database service.
Once traffic levels stabilized and resource utilization returned to normal baseline levels, the previously drained nodes were restored to active service, successfully restoring normal operations.
## Description of Impact
On 08 October, 2026, from 04:00 to 16:30 US/Pacific, customers utilizing the us-central1 region experienced elevated latency and error rates during Cloud Storage upload and write operations.
\* Customers primarily observed HTTP 503 UNAVAILABLE errors on WriteObject operations and client-side timeouts.
\* A minor impact was also observed on read operations during this timeframe.
\* Cloud Storage operations in all other regions, as well as all other Google Cloud services, remained unaffected by this specific event.

### 2026-10-14 07:15 UTC: resolved
## Incident Report
## Date/Time of the Issue (All time US/Pacific)
\*\*Incident First Occurrence\*\*
Incident Start: 08 October 2026 04:00
Incident End: 08 October 2026 16:30
Duration: 12 hours, 30 minutes
\*\*Incident Recurrence\*\*
Recurrence Start: 09 October 2026 04:05
Recurrence End: 09 October 2026 09:46
Duration: 5 hours, 41 minutes
\*\*Total Duration:\*\* 18 hours, 11 minutes
## Summary
On Thursday, 08 October 2026, Google Cloud Storage experienced elevated write latency and write error rates while performing upload or write operations in the us-central1 region for a duration of 12 hours, 30 minutes. This was followed by a recurrence on Friday, 09 October 2026 in the us-central1-b zone for a duration of 5 hours, 41 minutes. We are taking immediate steps to ensure this doesn’t happen again.
## Root Cause
Google Cloud Storage relies on a highly distributed backend architecture to process and store incoming data. During the incident window, specific storage backend nodes within the us-central1 region experienced a localized capacity shortfall due to increased traffic.
The sequence of events leading to customer impact was as follows:
\* A traffic sorting optimization configuration update to the Google Cloud Storage load balancing layer intended to address localized capacity constraints caused severe resource exhaustion on specific storage backend nodes in the affected region by inadvertently bypassing the standard capacity-aware routing logic, resulting in a severe load imbalance.
\* Consequently, a small fraction of storage backend nodes in the us-central1 region received an overwhelming proportion of incoming write traffic despite having low available serving capacity. This concentration of traffic led to resource exhaustion on the affected backend servers causing backend services handling object data ingestion to begin timing out.
\* Because the underlying instances could not process the high volume of requests quickly enough, the incoming upload and write requests routed to these nodes experienced elevated latency and failed to complete, resulting in errors surfaced to customers.
\* Concurrently, a separate issue with the underlying database service contributed to additional metadata processing errors during a portion of the incident window.
\* The recurrence of the issue on October 9 was caused by an incomplete rollback of an upload planner feature, which broke the load balancing mechanism and overloaded a few smaller storage backend nodes.
## Remediation and Prevention
The issue was initially detected on 08 October 2026 at 04:50 by Google engineering teams actively monitoring system telemetry early in the incident window. 
To mitigate the issue, Google engineers executed the following step-by-step strategy:
\* Engineers initially attempted to dynamically allocate additional emergency capacity to the affected region, but this was blocked by systemic regional capacity limits.
\* To relieve immediate pressure, engineers selectively drained traffic from the most overloaded storage backend nodes.
\* A configuration change was deployed to disable the traffic sorting optimization, significantly reducing resource overhead on the storage backend.
\* For the concurrent metadata issue, engineers rolled back a recent update to the underlying metadata database service.
\* While these steps provided temporary relief, a recurrence of the load imbalance required further traffic redirection and draining of affected storage components. The incident was permanently resolved when engineering fully reverted the problematic load balancing configuration change, restoring the previous capacity-aware routing behavior and allowing traffic to distribute evenly across the region.
Once traffic levels stabilized and resource utilization returned to normal baseline levels, the previously drained nodes were restored to active service, successfully restoring normal operations.
\*\*Preventative Actions:\*\*
To ensure this issue does not recur, we are implementing the followin

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