Mixpanel Incident History

1. resolvedOct 21 · 20:15 UTC

   This incident has been resolved.

Reported by Mixpanel on their status page.

1. postmortemOct 24 · 01:58 UTC

   Mixpanel RCA: Requests to decide.mixpanel.com Failed, October 15–21, 2026

   Summary

   From Oct 15, 2026 to Oct 21, 2026, requests sent to decide.mixpanel.com and api-decide.mixpanel.com failed.

   This affected customers who sent event tracking, profile updates, or feature flag requests to this hostname, usually through a proxy.

   Events sent to this domain during this window were not received by Mixpanel and this data cannot be restored by Mixpanel.

   Traffic sent to api.mixpanel.com, api-js.mixpanel.com, api-eu.mixpanel.com, and api-in.mixpanel.com were not affected.

   Service on this hostname was unintentionally impacted while we were removing the /decide endpoint infrastructure. The hostnames were treated as part of the endpoint due to an incorrect understanding of system dependencies. To prevent this class of issue, we are adding traffic monitoring for the decide.mixpanel.com and api-decide.mixpanel.com hostnames. We will also require confirmed zero traffic at the hostname level before any hostname is removed.

   We have since restored service on decide.mixpanel.com .

   What happened

   Older Mixpanel SDKs called the /decide endpoint to fetch configuration for Legacy Automatically Tracked Mobile Events. We announced the endpoint’s retirement, and for some time /decide has returned a 410 response.

   Separately, decide.mixpanel.com and api-decide.mixpanel.com acted as aliases for our standard API hostnames. For example, decide.mixpanel.com/track ingested events the same way api-js.mixpanel.com/track does. Some customers had set up proxies or SDK configurations to send their traffic to these hostnames.

   On October 15 at 7:40 PM CDT, during the final cleanup of the /decide endpoint, we removed the DNS records for decide.mixpanel.com and api-decide.mixpanel.com and removed both hostnames from our load balancer.

   Before making the change, we confirmed that traffic to the /decide endpoint had dropped to zero. However, our monitoring measured traffic by endpoint rather than by hostname. It therefore did not show that other requests, such as /track and /flags, were still reaching Mixpanel through these hostnames.

   From then on, all requests to this hostname failed, including endpoints such as /track, /engage, /groups, and /flags.

   • Events and Profiles: Events, Profiles, and any data intended for Ingestion API endpoints to these hostnames during this window never reached Mixpanel, so we do not have a copy to restore. If you retained this data elsewhere, such as in proxy logs or your data warehouse, you can re-send it to Ingestion API’s /import, /engage, and /groups.
   • Feature flags: Feature flag requests sent to these hostnames failed. SDKs served the last stored variant if one existed, or otherwise the fallback value configured in your code.

   Timeline (Central Time, October 2026)

   • October 15, 7:40 PM CDT: The hostname removal is applied. Requests to decide.mixpanel.com and api-decide.mixpanel.com begin failing.
   • October 16, 5:22 AM CDT: We receive the first customer report. It is initially understood to be related to the planned /decide retirement.
   • October 21, 11:42 AM CDT: Following an increase in customer reports about tracking failing for proxies, we identify the hostname removal as the cause.
   • October 21, 12:26 PM CDT: We restore the hostnames. /decide remains retired.
   • October 21, 1:51 PM CDT: We confirm traffic to the restored hostnames has recovered.
   • October 21, 8:34 PM CDT: The incident is resolved.

   Root cause

   1. During the /decide retirement, decide.mixpanel.com and api-decide.mixpanel.com were unintentionally removed.
   2. These hostnames had been configured to accept all API traffic, not only /decide requests, and this behavior was undocumented.
   3. Our monitoring tracked traffic to the /decide endpoint but not to these hostnames, so pre-change checks did not show that other traffic was still active.
   4. Because the hostnames and the retired endpoint share a name, early customer reports were initially interpreted as expected effects of the announced /decide retirement. This delayed escalation.

   What we’re changing

   • Monitoring and alerting: We are adding traffic and error-rate monitoring and alerting for decide.mixpanel.com and api-decide.mixpanel.com, so failures are detected automatically rather than through customer reports.
   • Hostname audit: We are auditing all public API hostnames and routing aliases for similar undocumented entry points, and we will review new hostnames and aliases before they go live. We are also tracking traffic that arrives on any unexpected hostname.
   • Safer removals: Before any future change to a public hostname, we will confirm zero traffic at the hostname level, and we will identify and contact any projects still using it.
   • Customer communication: We will give customers advance notice of material infrastructure changes that affect public hostnames, including publishing them on a timeline in our changelog.

   Already deployed:

   • Restored decide.mixpanel.com and api-decide.mixpanel.com
   • /decide remains retired

   Common questions

   • Was my data affected? Only if your SDK or proxy sent requests to decide.mixpanel.com or api-decide.mixpanel.com between October 15 and October 21. Data sent there during that window were not received and cannot be restored by Mixpanel. If you retained a copy of that data, you can re-send it to Mixpanel using our Ingestion API endpoints such as /import for events.
   • Do I need to change anything? No, the domains work again. We recommend using api.mixpanel.com (or api-eu.mixpanel.com / api-in.mixpanel.com for EU and India data residency) as your API domain.
   • Is /decide coming back? No. It remains retired as announced, and it is separate from the decide.mixpanel.com hostname.

   We’re sorry for the disruption. If you have questions about your project, please contact your account team or Mixpanel Support.

Reported by Mixpanel on their status page.

1. ResolvedOct 22 · 01:34 UTC

   This incident has been resolved.

Reported by Mixpanel on their status page.

1. resolvedOct 9 · 00:22 UTC

   This incident has been resolved. The upstream issue with our cloud storage provider has been fixed, and our ingestion pipeline has been operating normally with no active delays. No events were lost throughout this incident, all affected data was fully reprocessed. Thank you for your patience throughout this incident.

Reported by Mixpanel on their status page.

1. ResolvedOct 9 · 00:22 UTC

   This incident has been resolved. The upstream issue with our cloud storage provider has been fixed, and our ingestion pipeline has been operating normally with no active delays. No events were lost throughout this incident, all affected data was fully reprocessed.Thank you for your patience throughout this incident.

Reported by Mixpanel on their status page.