Interview Questions for SRE -- Includes Scenario base questions

SRE Interview preparation guide/ Starting point 

Sections as below 

1. SRE Interview Questions
2. SRE Scenario Base Questions
3. References for self-learning

SRE Interview Questions

Question 1: What is Site Reliability Engineering (SRE)? 

Answer: Site Reliability Engineering (SRE) is a discipline that combines software engineering and systems administration to build and operate large-scale, reliable, and scalable software systems. SREs focus on creating automated solutions to monitor, manage, and maintain these systems, ensuring their availability, performance, and reliability.

Question 2: Can you explain the concept of "Error Budget" in SRE?

Answer: Error Budget is a critical concept in SRE. It represents the acceptable amount of downtime or errors that a service can experience within a specific time frame (usually a month). This concept helps balance the trade-off between system reliability and innovation. If the error rate or downtime exceeds the defined budget, development efforts are temporarily shifted from building new features to improving reliability until the error budget is restored.

Question 3: How does SRE differ from traditional operations or system administration? 

Answer: Traditional operations often focus on manual tasks, reactive problem-solving, and firefighting. SRE, on the other hand, emphasizes automation, software engineering, proactive monitoring, and the use of well-defined Service Level Objectives (SLOs) and Service Level Indicators (SLIs) to ensure system reliability. SREs work to prevent incidents rather than just responding to them.

Question 4: What are SLIs, SLOs, and SLAs? 

Answer:

• SLI (Service Level Indicator): A measurable metric that indicates the performance of a service, such as response time, availability, or error rate.
• SLO (Service Level Objective): A target value or range for an SLI that defines the acceptable level of service performance. SLOs help set customer expectations and guide engineering efforts.
• SLA (Service Level Agreement): A formal agreement between the service provider and its customers, outlining the guaranteed level of service availability and performance. SLAs are often based on SLOs.

Question 5: Describe the concept of "Toil" in SRE. 

Answer: Toil refers to repetitive, manual, and operational work that doesn't provide long-term value and is prone to human error. SREs aim to minimize toil by automating such tasks to free up time for more strategic and impactful work, such as improving reliability, efficiency, and innovation.

Question 6: How do you approach capacity planning for a service? 

Answer: Capacity planning involves predicting resource needs for a service to handle current and future loads. An SRE would typically:

• Gather historical usage data and project future growth.
• Define performance SLIs to understand the service's limits.
• Conduct load testing to identify bottlenecks and resource requirements.
• Monitor resource utilization to ensure the service operates within its capacity limits.
• Use auto-scaling mechanisms to adapt to varying workloads.

Question 7: Can you explain the process of incident management in SRE? 

Answer: Incident management involves identifying, responding to, mitigating, and learning from service disruptions. SREs follow a structured approach:

• Detection: Monitoring tools and automated alerts identify anomalies or deviations from normal behavior.
• Response: SREs quickly respond to incidents, involving the right team members to mitigate the issue and minimize impact.
• Mitigation: Immediate actions are taken to restore service. Long-term fixes are implemented to prevent recurrence.
• Post-Incident Review: SREs conduct a thorough review to understand the root cause, assess the response process, and identify improvements for the future.

Question 8: How do you ensure reliability in a microservices architecture? 

Answer: In a microservices architecture, SREs can ensure reliability by:

• Setting SLIs and SLOs for each microservice.
• Implementing effective service discovery and load balancing mechanisms.
• Designing for graceful degradation and fallback mechanisms.
• Implementing circuit breakers to prevent cascading failures.
• Applying chaos engineering to simulate failures and assess system resilience.

Remember that these answers are meant to serve as a starting point for your interview preparation. It's important to understand the concepts deeply and be ready to provide detailed explanations based on your experience and understanding. Additionally, interviewers might ask scenario-based questions to assess your problem-solving skills and real-world application of SRE principles.

 

SRE Scenario Base Questions

Scenario 1: Incident Response and Mitigation Question: Imagine you're on-call and receive an alert that a critical service is experiencing high latency. What steps would you take to handle this incident? 

Answer: I would start by acknowledging the alert and immediately checking the service's monitoring dashboard to understand the extent of the latency issue. If it's impacting users, I would escalate the incident to the necessary team members. I would also:

1. Collect relevant logs and metrics to diagnose the root cause.
2. Perform targeted load testing or traffic isolation to prevent further degradation.
3. Implement any necessary fixes or mitigations, possibly by scaling resources or diverting traffic.
4. Communicate transparently with stakeholders about the incident and the actions being taken.
5. Conduct a post-incident review to understand what caused the latency and identify improvements for the future.

Scenario 2: Scaling and Capacity Planning Question: Your application is about to be featured on a popular TV show, and you expect a sudden surge in traffic. How would you ensure your system can handle the increased load? 

Answer: To handle the traffic surge:

1. Utilize auto-scaling mechanisms to automatically provision additional resources as needed.
2. Conduct load testing in advance to identify potential bottlenecks and tune the system accordingly.
3. Implement caching and content delivery networks (CDNs) to offload static content.
4. Configure rate limiting and traffic shaping to control incoming requests and prioritize critical functionalities.
5. Prepare a rollback plan in case unexpected issues arise.

Scenario 3: Maintaining High Availability Question: How would you design your system to ensure high availability across different regions in case of a regional data center outage? 

Answer: To ensure high availability across regions:

1. Deploy the application across multiple geographic regions to distribute user traffic.
2. Utilize multi-region load balancers to route traffic to healthy regions.
3. Set up active-active replication for databases and data storage.
4. Implement a failover mechanism to automatically redirect traffic to an available region in case of an outage.
5. Continuously monitor the health and availability of each region and perform regular disaster recovery drills.

Scenario 4: Toil Reduction and Automation Question: Give an example of a toil-reduction task you've automated in a previous role. 

Answer: In a previous role, I automated the process of certificate renewal for SSL/TLS certificates. Rather than manually tracking expiry dates and renewing certificates, I created a script that:

1. Monitored the expiration dates of certificates.
2. Automatically requested renewal and obtained new certificates from the certificate authority.
3. Deployed the renewed certificates to the appropriate services without human intervention. This automation reduced the risk of forgetting to renew certificates and saved valuable time spent on manual tasks.

Scenario 5: Incident Post-Mortem and Learning Question: Following a major incident, how would you conduct a post-mortem to ensure the issue doesn't recur? 

Answer: To conduct a post-mortem:

1. Assemble a cross-functional team including those directly involved in the incident.
2. Document the timeline of events, actions taken, and the impact on users.
3. Analyze the root cause using available data, logs, and metrics.
4. Identify contributing factors, whether they were technical, procedural, or organizational.
5. Propose actionable steps to prevent similar incidents in the future, such as improving monitoring, enhancing automated response, or revising processes.
6. Share the findings and action items with the broader team and stakeholders.

Remember, interviewers might be looking for not only your technical expertise but also your problem-solving skills, communication abilities, and your approach to collaborating with teams under pressure. It's important to emphasize your ability to learn from incidents and iterate on systems for continuous improvement.

References for self-learning

Here are some excellent resources to help you learn more about Site Reliability Engineering (SRE) and enhance your knowledge in this field:

Books:

1. "Site Reliability Engineering: How Google Runs Production Systems" by Niall Richard Murphy, Betsy Beyer, Chris Jones, and Jennifer Petoff - This book is considered the definitive guide to SRE and provides insights into Google's approach to maintaining large-scale systems.
2. "The Site Reliability Workbook: Practical Ways to Implement SRE" by Niall Richard Murphy, David K. Rensin, Betsy Beyer, and Kent Kawahara - This workbook is a companion to the first book and offers practical exercises, examples, and case studies to help you implement SRE principles.
3. "Seeking SRE: Conversations About Running Production Systems at Scale" edited by David N. Blank-Edelman - This book compiles interviews and discussions with SRE practitioners from various companies, sharing real-world experiences and insights.

Online Resources:

1. Google SRE Website: Google's own SRE website provides a wealth of resources, including articles, videos, and documentation, giving you insights into their approach to reliability engineering. Google SRE
2. The SRE Book's Website: The official website for the "Site Reliability Engineering" book series includes additional resources, updates, and links to related materials. The SRE Book
3. LinkedIn Learning (formerly Lynda.com): This platform offers various SRE-related courses, such as "Introduction to Site Reliability Engineering" and "DevOps Foundations: Site Reliability Engineering."
4. Coursera: Look for courses related to SRE, DevOps, and reliability engineering on Coursera. These courses are often offered by top universities and industry professionals.
5. YouTube: Search for SRE-related talks and presentations from conferences like SREcon, DevOpsDays, and various technology conferences. Google's official YouTube channel also hosts talks about SRE.

Blogs and Articles:

1. The SRE Weekly Newsletter: A curated collection of SRE-related articles, blog posts, and discussions from around the web.
2. Medium SRE Tag: Medium hosts a variety of articles written by SRE practitioners, sharing their experiences and insights.
3. The New Stack: This platform often publishes articles on SRE, DevOps, and related topics.

Community and Conferences:

1. SREcon: An annual conference organized by USENIX that focuses on Site Reliability Engineering. Attending SREcon can provide you with networking opportunities and exposure to the latest industry practices.
2. DevOpsDays: These community-driven events often feature talks and discussions about SRE, DevOps, and related topics.

Remember that the field of SRE is continuously evolving, so staying updated with the latest trends and practices is crucial. Engaging with online communities, attending conferences, and actively participating in discussions can greatly enhance your learning journey.

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