This post comes from a real outage note I wrote after a FusionAuth service failure in a managed Kubernetes environment.

I am keeping it because it captures a kind of infrastructure lesson that is easy to talk around after the fact: sometimes the outage is not caused by one bad command, but by a chain of assumptions that only become visible once the platform is already down.

What Happened

The short version is this:

  • the cluster provider forced a Kubernetes upgrade from 1.27 to 1.28
  • the actual upgrade window began on June 17, 2024
  • by June 18, 2024, the volume replicas backing the environment had failed to recover cleanly
  • the FusionAuth cluster that depended on that storage lost its data

This was not a normal application bug. It was an infrastructure and storage failure with application-level consequences.

The Trigger

The first important event was the provider notification. An e-mail had gone out on Saturday, June 15, 2024, saying the managed Kubernetes version would be upgraded from 1.27 to 1.28.

The actual upgrade took place on June 17, 2024.

In hindsight, that notice should have triggered a more aggressive pre-upgrade review. At the time, it did not get the attention it needed.

Where the Failure Showed Up

The actual outage became visible on June 18, 2024, when the storage layer did not recover cleanly after the rolling upgrade behavior across the nodes.

The environment had been using Longhorn CSI for storage because it was close to the setup we had used in earlier clusters and fit the migration path we were under pressure to complete.

That choice became the center of the failure. Once the storage layer did not come back correctly, FusionAuth was no longer just degraded. It was effectively operating without the data it needed.

The Hard Part

The hardest part of the incident was not understanding that the service was down. It was understanding how limited the recovery options really were.

There was a backup gap.

At the time, the available backup situation was weaker than it should have been:

  • one backup path depended on infrastructure that had already been decommissioned
  • another useful copy was not immediately accessible
  • the migration workload from earlier environments had already pushed backup hardening behind other urgent tasks

That meant recovery was no longer a clean “restore the latest copy and move on” operation.

It became a tradeoff between:

  • restoring quickly with limited historical data
  • waiting longer while hunting for a better backup that might not materialize

The Decision

By June 19, 2024, the best usable copy we could identify was older than we wanted.

At that point, the decision was to restore service availability as quickly as possible instead of waiting for a perfect recovery source that was not realistically within reach.

This is one of the uncomfortable realities of incident response: sometimes the technically incomplete recovery is still the operationally correct decision.

What Changed Afterward

The incident did lead to concrete changes.

After the outage:

  • we moved away from the failing storage approach for that environment
  • we added a temporary backup destination in the provider environment itself
  • we added backup scripts to generate copies from our side
  • we started pushing harder on monitoring and logging visibility

Those steps do not erase the outage, but they do matter. A postmortem only helps if it changes the next version of the system.

What I Took From It

The main lesson was not “check your e-mail more carefully”, even though that would have helped.

The deeper lesson was this:

If you are running stateful identity services on top of managed Kubernetes, then upgrade notices, storage compatibility, recovery procedures, and backup reachability are all part of the same system.

You cannot treat them as separate concerns.

The outage happened at the point where those concerns overlapped:

  • managed upgrade pressure
  • storage assumptions
  • incomplete backup coverage
  • migration fatigue

That combination is what made the incident expensive.

Closing Thought

I like keeping notes like this because they preserve the part people often forget once the service is back up. Not the command that fixed the symptom, but the chain of operational decisions that made the outage possible in the first place.

That is usually the part worth writing about.