SRE Interview questions

 1. Explain the concept of SLO, SLI, and SLA. How are they interconnected?

   - Answer: Service Level Objectives (SLOs) define a target level of service. Service Level Indicators (SLIs) are metrics that measure the service, while Service Level Agreements (SLAs) are the agreements about the level of service. They are interconnected as SLIs are used to measure the achievement of SLOs, which, when met, ensure compliance with SLAs.

2. What is the significance of error budgets in an SRE context? How do you calculate and utilize error budgets?

   - Answer: Error budgets represent the allowed error or downtime within a service before it impacts users. It quantifies how reliable the service needs to be. They are calculated by subtracting the error budget from 100%. Utilizing error budgets helps prioritize improvements and allows for controlled risk-taking during development.

3. Describe how you'd implement a service monitoring system from scratch.

   - Answer: I'd start by identifying key metrics (like latency, error rates, etc.) and setting up monitoring tools (like Prometheus, Grafana). Then, I'd create alerting rules based on these metrics and establish dashboards for visualization. Additionally, implementing logging and tracing tools helps in comprehensive system monitoring.

4. Discuss the importance of chaos engineering in maintaining system reliability. Provide examples of chaos engineering experiments.

   - Answer: Chaos engineering involves deliberately injecting failures into a system to test its resilience. It helps identify weaknesses and improve system robustness. For instance, simulating network outages, shutting down services randomly, or introducing latency to observe system behavior.

5. How do you handle incidents in a production environment? Explain your incident response process and any tools you might use.

   - Answer: Our incident response involves detecting issues through monitoring, assigning severity levels, and activating incident response teams. We use incident management tools like PagerDuty or OpsGenie, follow predefined runbooks, conduct post-incident reviews, and update documentation.

6. Explain in detail the principles of "Error Budgets" and how it influences decision-making in an SRE team.

   - Answer: Error budgets define the acceptable failure rate. It allows teams to balance stability and innovation. When the error budget is consumed, teams focus on reliability over new features. This principle guides the allocation of engineering resources for improvements.

7. Design an automated incident response system that can handle complex failures and prioritize critical incidents.

   - Answer: I'd create an incident orchestration system that uses machine learning to predict incident severity. It would automatically trigger predefined response actions based on severity, escalating critical incidents to on-call teams and documenting incident resolution steps for future reference.

8. Discuss the role of service meshes like Istio in improving service observability and reliability.

   - Answer: Service meshes like Istio manage communication between microservices, offering observability through metrics, logging, and tracing. They enhance reliability by providing fault tolerance, traffic control, and security features like mutual TLS.

9. How would you implement a zero-downtime deployment strategy for a large-scale microservices-based application?

   - Answer: Utilize blue-green or canary deployments, ensuring multiple instances of each microservice. Deploy gradually, routing a portion of traffic to new versions, validating their performance, and gradually shifting all traffic to the new version.

10. Describe the process of setting up a multi-region, active-active architecture for disaster recovery and high availability.

   - Answer: Implement redundant infrastructure in multiple regions, distribute traffic across regions using DNS or a global load balancer, and replicate data between regions. Use health checks to automatically reroute traffic in case of failures.