🧠Site Reliability Engineer (SRE) Interview Questions

In this article we will cover the top 25 SRE interview questions to help you prepare for you next SRE interview.

As customer demand for reliable and high-performing services continues to grow, the role of Site Reliability Engineers (SRE’s) continues to grow in importance. Whether you are a seasoned SRE or a recent graduate preparing for an SRE interview, these questions will be invaluable for determining your level of expertise and understanding where you need to grow. This article will guide you through some of the key questions you might encounter in an SRE interview, helping you better understand what to expect and how to prepare effectively. We have also provided valuable information and trusted sources to help you grow your knowledge in the areas you feel could use more in-depth reading. Whether you're new to the field or looking to advance your career, these questions will help you prepare for your next SRE interview.

Top 25 SRE Interview Questions (and Answers)

These SRE interview questions and answers are designed to help you prepare for an SRE interview by identifying key areas where knowledge on subjects may be lacking. We will cover the following:

SRE Interview Questions:

SRE Interview Questions Answers and Resources

1. Can you explain what Site Reliability Engineering (SRE) is?

Site Reliability Engineering (SRE) is a discipline that applies software engineering principles to infrastructure and operations to create scalable and highly reliable software systems.

2. What are the key principles of SRE?

  • Embracing and managing risk - Utilizing error budget to implement and test new features.

  • Maintaining Service Level Objectives - Tracking and comparing SLIs to your SLOs to ensure you meet your SLA.

  • Eliminating toil - Reducing repetitive mundane tasks that can be automated, allowing for better use of time.

  • Monitoring - Keeping track of systems and performance to address issues before they become real problems.

  • Automation - Implementing automation to reduce toil.

  • Release engineering - The technical aspects of compiling, assembling, and delivering source code.

  • Simplicity - Its easier to understand the effect of small simple changes over large batch changes.

For a more in-depth information on the key principles of SRE can be found here.

3. What are the 4 Golden Signals of SRE?

  • Latency - The amount of time your services take to fulfill a request.

  • Traffic - The number of requests your service receives.

  • Errors - The number of unsuccessful requests both overall and at specific end points.

  • Saturation - The utilization of resources in comparison to their capacity.

For a more in-depth information on the 4 Golden Signals of SRE can be found here.

4. How do you define and measure Service Level Objectives (SLOs) and Service Level Indicators (SLIs)?

SLOs are typically written and set by product managers to meet or exceed promises made in the company's SLA. SLOs are typically written to give teams an error budget and room for experimentation. SLIs are the actual measured performance of the service being provided indicating whether the performance is meeting SLOs and SLAs. For additional learning on this topic, read our in-depth SLA, SLO, and SLI resources.

5. What is error budget, and what role does it play in SRE?

Error budget is the difference in performance between your SLA and SLO that allows for downtime, performance issues, and feature experimentation.

6. SRE vs DevOps: What's the difference?

SRE focuses on engineering solutions for system reliability and performance, while DevOps emphasizes collaborative practices to enhance and streamline the software development and delivery process.

7. What is the importance of monitoring and alerting in SRE? What tools have you used?

Monitoring and alerting are important in Site Reliability Engineering (SRE) because they help identify potential issues before they cause outages. Monitoring tools provide real-time insights into system performance, infrastructure health, and user behavior. Monitoring Tools Include:

Alerting Tools Include:

8. What is the difference between logging, monitoring, and tracing?

  • Logging - captures detailed records of events within a system, which is useful for diagnosing specific issues.

  • Monitoring - continuously tracks system metrics for real-time health and performance insights.

  • Tracing - follows the flow of requests through a system to pinpoint bottlenecks and understand interactions.

9. Explain DNS and its importance.

DNS or Domain Name System translates domain names into IP addresses so browsers can load webpages. DNS servers allow the average user to type words into their browser and find the pages they are looking for without having a phonebook of IP addresses.

10. How do you prioritize which alerts to respond to first during an incident?

The first step to prioritizing alerts is to understand the severity level of the incident, who it affects, and what kind of impact it will have on your customers or systems. After determining the severity level, you can prioritize alerts starting from a SEV-1 level (highest, greatest impact) down to a SEV-5 (lowest, smallest impact).

11. What is Chaos Engineering?

Chaos Engineering is a methodical approach to discovering failures before they lead to outages. By proactively testing how a system responds to stress, you can pinpoint and resolve failures before they become problems that affect your customers and systems. Chaos Monkey is a popular tool used in Chaos Engineering.

12. How do you handle capacity planning and scaling for high-traffic applications?

  • Use load balancing - Distribute requests across multiple servers, optimizing resource utilization.

  • Cache frequently accessed data - Improve response time and scalability by storing frequently accessed data.

  • Automate testing - Stress test your system to identify bottlenecks in performance. Use continuous integration tools (like GitHub Actions) to automatically test code changes.

  • Monitor systems - Utilize APM tools to provide real-time insight into your system’s performance and health to detect issues before they affect customers.

  • Design your system to scale - Scale your system up or down to meet the needs of traffic to maintain performance.

13. What are containers on a server?

Containers are self-contained software packages that can run in any environment without any modifications. They virtualize the operating system and are capable of running in various settings, including private data centers and public clouds. Docker is a common containerization tool.

14. What is database sharding?

Database sharding involves distributing a large database across multiple machines. Since a single machine or database server can only handle a limited amount of data, sharding splits the data into smaller logical chunks called shards and stores them across multiple database servers to overcome this limitation.

15. How will you secure your Docker containers?

  • Avoid running Docker containers with root permissions - While this may make dealing with permission management easier, you open up the container to risk.

  • Use secure container registries - Utilizing secure registries like Docker Trusted Registry helps prevent potential security risks.

  • Limit container resource usage - This helps prevent attacks on your systems from resource exhaustion from those looking to disrupt your service.

  • Scan images - Scanning images regularly for vulnerabilities helps prevent security risks. Tools like Snyk can help with automated container scanning.

  • Monitor containers - Utilize monitoring tools like (Prometheus or Datadog) to monitor your containers, gaining visibility and observability.

16. What is observability?

The concept of observability refers to the ability to understand the internal state of a software system based on its external outputs. It involves using data and insights from monitoring to understand the system's health and performance. Observability methods include USE and RED.

17. What is DHCP?

DHCP or Dynamic Host Configuration Protocol is the protocol that provides an Internet Protocol (IP) host with its IP address as well as any additional necessary configurations.

18. Can you explain the difference between a blue-green and canary deployment?

Blue-green deployment involves running two identical environments (blue and green). One environment handles live traffic, while the other is used for testing new releases before directing traffic to it, making it easy to revert if necessary. In contrast, canary deployment introduces the new version gradually to a small group of users before a full release, enabling step-by-step validation and reducing the impact of any potential issues.

19. How do you approach security and compliance in an SRE Role?

  • Implement access controls - Ensure only those you trust have access to sensitive systems and information.

  • Conduct regular security checks - Identify vulnerabilities and risks often and early.

  • Monitor and log activity - Proactively monitor systems and logs for suspicious activities.

  • Implement backups and disaster recovery - Having backups helps you recover systems quickly and effectively.

For more in-depth learning on SRE security and best practices, read β€œSecurity with SRE.”

20. What is the difference between TCP and UDP?

Transmission control protocol or TCP is a reliable connection-based protocol. While more reliable than UDP, data transfers are slower. User Datagram Protocol or UDP is a less reliable connectionless protocol that works faster than TCP. You can think of TCP as a β€œhandshake” communication technology, and UDP as a ”broadcast/shout to the ether” communication technology.

21. Explain the difference between IaaS, PaaS and SaaS.

  • IaaS (Infrastructure as a Service) - provides virtualized computing resources over the internet, giving users control over the operating systems, storage, and deployed applications. Examples include AWS, Azure, and Google Cloud.

  • PaaS (Platform as a Service) - offers a platform for developers to build, run, and manage applications without managing the underlying infrastructure. Examples include Heroku, Fly.io, and Render.

  • SaaS (Software as a Service) - delivers fully functional software applications over the internet, accessible via web browsers, with the provider handling all underlying infrastructure and maintenance. Examples include PagerTree, Netflix, and Google Sheets.

22. What is SSH, and how does it work?

The Secure Shell (SSH) protocol provides a secure way to send commands to a computer over an unsecured network. It uses cryptography to authenticate and encrypt connections between devices.

23. What is toil reduction, and how is it achieved?

Toil is a term used to describe manual, repetitive, and tedious tasks that engineers perform in production environments. Toil reduction is the process of reducing the amount of time spent on tasks that are considered toil. This can be achieved through process automation.

24. What is white-box monitoring?

White-box monitoring is a method of monitoring the internal metrics of applications that run on a server when you can access its source code.

25. What is black-box monitoring?

Black box monitoring is a type of application monitoring that focuses on an application's external behavior without needing access to its source code.

Additional SRE Interview Questions to Consider

Not all questions will have straightforward black-and-white answers. Some questions may require you to think of your previous experience or critically think about difficult situations. The following questions will help you consider your previous experiences or what you might do in a specific situation. Taking the time to think about your answers and write them down will help you prepare for any questions that may arise in your SRE interview.

  • Describe a time when you had to handle a major incident. What steps did you take to resolve it?

  • Describe a scenario where you improved the reliability or performance of a system. What was your approach?

  • What experience do you have with automation in SRE? Can you provide an example of a process you automated?

  • Describe a time when you had to work closely with developers to improve a service. How did you facilitate this collaboration?

  • What are some common challenges you have faced in maintaining system reliability, and how did you overcome them?

  • How do you stay current with the latest trends and technologies in SRE?

  • Can you share an example of how you used data to make a decision that improved system reliability or performance?

  • How do you ensure that deployments are reliable and do not negatively impact the system's availability?

  • How do you balance the need for rapid deployment with the need for system stability?

  • What is your experience with containerization and orchestration tools like Docker and Kubernetes?

Your Next SRE Role

At some point, every system will fail, the real question is how we prevent unnecessary failures, downtime, and customer frustration. As a Site Reliability Engineer, you’ll work towards improving systems, implementing tools, and increasing site reliability. The SRE role continues to grow in demand, as does the pool of candidates. Putting time and effort into preparing for your SRE interview could give you the edge you need to stand out above other candidates for any role you apply for.

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