What step should you take if a recently updated container image in GKE causes issues, but the specific change is unknown?

Choosing to alter the deployment to point to the sha256 digest of the previously working container is a robust approach to resolving issues caused by a recently updated container image. The sha256 digest provides an immutable identifier for the specific version of the container image, ensuring that the deployment will roll back to exactly the same code and configuration that was previously functioning correctly.

When you use the sha256 digest, you are not relying on tags, which can sometimes be updated or overridden. Tags like "latest" can lead to ambiguity and unpredictability since they do not guarantee the same image will be pulled over time. By using the digest, you create clarity and certainty in your deployment.

This method also facilitates better reproducibility in environments because the digest uniquely identifies the image, thus significantly reducing the chances of reintroducing the issues that were present in the updated image.

While other options involve returning to a previous image version, they either rely on the mutable naming conventions of tags—which can be misleading—or involve recreating images, which adds unnecessary complexity in terms of build, management, and deployment. The sha256 method ensures a precise rollback to what is known to be stable without additional overhead.