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https://cloud.google.com/binary-authorization

Binary Authorization is a deploy-time security control that ensures only trusted container images are deployed on Google Kubernetes Engine (GKE) or Cloud Run. With Binary Authorization, you can require images to be signed by trusted authorities during the development process and then enforce signature validation when deploying. By enforcing validation, you can gain tighter control over your container environment by ensuring only verified images are integrated into the build-and-release process.

https://sre.google/workbook/implementing-slos/

In the SRE principles book, it's recommended treating the SLI as the ratio of two numbers: the number of good events divided by the total number of events. For example: Number of successful HTTP requests / total HTTP requests (success rate)

Comprehensive and Detailed Explanation:

In Google’s Site Reliability Engineering (SRE) practices, an error budget defines the acceptable level of failure before new feature deployments should pause. If a service exceeds its error budget, the correct approach is to:

Notify the product team that the error budget is depleted.

Negotiate a launch freeze or decide if the team can tolerate slightly degraded performance.

????Why not other options?

A (Ensure all tests pass and proceed)❌→ Testing cannot guarantee stability when the error budget is already depleted.

C (Request additional error budget)❌→ Error budgets are not arbitrary; increasing them would defeat their purpose.

D (Reallocate SLOs from other areas)❌→ Error budgets should not be mixed across different SLOs, as this breaks reliability guarantees.

????Official Reference:

Google SRE: Error Budget Policy

Google Cloud SRE Principles

Comprehensive and Detailed Explanation:

Cloud Deploy is a GCP-native managed CI/CD tool for reliable and automated releases across environments.

Artifact Registry Cleanup Policy automates image retention and deletion of old images, reducing storage costs and avoiding clutter.

Rollback and rollback policies should be handled by Cloud Deploy, not manual interventions.

????Why not other options?

A❌→ Cloud Build jobs for cleanup are not scalable or automated compared to Artifact Registry policies.

B❌→ Cloud Service Mesh is not related to deployment rollbacks or image cleanup.

D❌→ Cloud Deploy provides better rollback management than a custom rollback pipeline.

????Official Reference:

Google Cloud Deploy Overview

Artifact Registry Cleanup Policy

Comprehensive and Detailed Explanation From SRE Principles:

This scenario presents a classic SRE conflict: maintaining reliability (as dictated by the exhausted error budget and deployment freeze) versus delivering an urgent business requirement. The error budget policy is there for a reason – to protect users from further instability.

A. Start the deployment of the feature immediately: This directly violates the established error budget policy and the deployment freeze. While the feature is urgent, deploying without caution when the system is already unstable (as indicated by the exhausted error budget) is highly risky and could exacerbate existing problems or introduce new ones, further impacting revenue and customer trust.

B. Delay the deployment of the feature until the error budget is replenished: This strictly adheres to the policy but might not be acceptable given the "urgently required by your largest customer" clause. SRE principles allow for reasoned exceptions and risk management, not just blind adherence if the business context is compelling enough and risks are managed.

C. Re-run the unit tests, and start the deployment of the feature if the tests pass: Unit tests are foundational but insufficient to guarantee a complex application will perform reliably in production, especially when the system is already indicating instability (exhausted error budget). Passing unit tests doesn't negate the risk signaled by the depleted error budget.

D. Deploy the feature to a subset of users, and gradually roll out to all users if there are no errors reported: This is the most balanced SRE approach in this situation. It acknowledges the urgency while attempting to mitigate risk:Risk Mitigation: A canary release (deploying to a small subset of users) limits the potential negative impact if the new feature introduces new errors or worsens existing instability.

Observation: It allows for careful monitoring of the new release in the production environment with real users.

Data-Driven Decision: The decision to proceed with a wider rollout is based on observed behavior ("if there are no errors reported"), not just assumptions.

Controlled Rollout: A gradual rollout allows for quick rollback if issues arise.

While an exhausted error budget signals a deployment freeze, critical business needs can sometimes necessitate a carefully managed exception. A canary release is a standard SRE technique for deploying changes with reduced risk, making it the most appropriate course of action when faced with such conflicting priorities. The team would also need to communicate clearly about the risks and the rationale for this exception. It's implied that this urgent feature might also fix existing issues or is critical enough to warrant the carefully managed risk.

Reference (Based on SRE principles from Google's SRE books and general practices):

Error Budgets: "The SRE Book" (Site Reliability Engineering: How Google Runs Production Systems) discusses error budgets and deployment freezes. An exhausted error budget typically means no more risky changes until reliability improves.

Canary Releases: This is a fundamental practice for safely deploying new versions. It's about testing in production with a small percentage of traffic.

Managing Risk: SRE is about managing risk, not eliminating it entirely. In situations like this, a calculated risk with strong mitigation (canary, monitoring, rollback plan) can be justified for critical business needs. The decision involves weighing the risk of deploying against the risk of not deploying the urgent feature.

Option D represents a pragmatic SRE approach to navigate this difficult situation by minimizing the blast radius of the change.

https://cloud.google.com/container-registry/docs/pushing-and-pulling

The best option for implementing the rollback actions is to update the Kubernetes Service to point to the previous Kubernetes Deployment. A Kubernetes Service is a resource that defines how to access a set of Pods. A Kubernetes Deployment is a resource that manages the creation and update of Pods. By using the blue/green deployment methodology, you can create two Deployments, one for the current version (blue) and one for the new version (green), and use a Service to switch traffic between them. If you need to rollback, you can update the Service to point to the previous Deployment (blue) and stop sending traffic to the new Deployment (green).

A change advisory board (CAB) is a traditional way of approving changes to a service, but it can slow down the software delivery performance and introduce bottlenecks. A better way to improve the speed and quality of changes is to use a peer-review based process for individual changes that is enforced at code check-in time and supported by automated tests. This way, developers can get fast feedback on the impact of their changes and catch any errors or bugs before they reach production. Additionally, the team’s development platform should enable developers to get fast feedback on the impact of their changes, such as using Cloud Code, Cloud Build, or Cloud Debugger.

The correct answer is B. Use shadow testing with continuous deployment.

Shadow testing is a deployment technique that involves routing a copy of the live traffic to a new version of the application, without affecting the production environment. This way, you can gather performance metrics and compare them with the current version, without exposing the new version to the users. Shadow testing can help you test against the full production load and identify any issues or bottlenecks before launching the new version. You can use continuous deployment to automate the process of deploying the new version after it passes the shadow testing.