Site Reliability Engineer (SRE) Interview Questions and Preparation Guide


Site Reliability Engineer Interview Preparation Guide and Tips (With Sample Questions and How to Answer)

Site reliability engineering (SREs) is gaining more traction in software development and IT. As a result, there are thousands of open positions for SREs in the U.S and worldwide as organizations across industries look to shore up the performance and reliability of their systems.

The concept of SRE was introduced by Benjamin Treynor in 2002 and was popularized through Google’s SRE eBook as an approach to service management. Historically, software engineers used to design code and hand it over to operations to deploy, maintain, and respond to incidents. However, with software development becoming faster and more complex, traditional software teams started having trouble keeping up. One side of the organization wants to deliver cutting-edge features quickly, while the other side wants to ensure they are secure, up, and stable. Developers want to release code frequently and rapidly, while IT operations are concerned about the application’s downtime.

SREs, integrate engineering experience with an innate drive to enhance existing systems and processes to design cutting-edge solutions to evolving challenges. Site Reliability Engineers oversee the software, and execution of the full technology stack plays an integral role in deploying and maintaining the software. It also improves the software to increase system reliability and performance. According to the SRE book, an SRE should spend half of its time on “ops” work and the other half doing development.

It is more challenging to prepare for SRE interviews than for some other IT roles as it is still a developing role in companies, even though it has its roots in traditional IT operations and DevOps. An efficient SRE needs to possess non-technical skills alongside tech prowess. We’ve put together the interview guide to help you prepare for your SRE interview.

What is a Site Reliability Engineer?

Site Reliability Engineer combines software engineering with IT to create highly reliable systems. SREs are responsible for the reliability of the full stack, from the front-end, customer-facing applications to the back-end database and hardware infrastructure.

Site reliability engineers help developers actively build services and functions to improve the resilience of people, processes, and technical systems. SREs contribute to the team’s overall productivity and the reliability of the team’s applications and infrastructure. SREs, apply SRE site principles to manage availability, latency, performance, efficiency, change management, monitoring, emergency response, and capacity planning. They also work as support engineers, leveraging monitoring, capacity, and optimizing automation tools.

SREs are tasked with ideating and implementing methods to enhance and automate operational tasks, thus streamlining development and deployment processes. SREs must have software development experience, but their primary strengths are network engineering, troubleshooting, deployment, and configurations.

Primary Roles and Responsibilities of an SRE

The SRE role is subjective regarding specific responsibilities as it is still developing as a specialized role. For example, SREs play a crucial role in software development and programming at some companies, while others focus more on operations.

The site Reliability Engineer acts as a bridge between development and operations teams. The work involves incorporating aspects of software engineering and applying them to resolve infrastructure and operations problems while creating scalable and highly reliable software systems.

SREs write and deploy code to improve the resilience of applications and infrastructure. They are also in charge of enhancing visibility into system health to gain deeper insights and prepare teams for incident response and remediation.

Site reliability engineers oversee the entire system, and they can quickly identify an incident’s root cause and actively resolve the problem.

Site reliability engineers are the end-all-be-all for system observability and incident response. The SRE team is equipped to see issues across the entire service and maintain context and historical information. As a result, SREs ensure accurate, detailed documentation, continuously improve the reliability of production systems, and share the knowledge across the teams, leading to a better understanding of how services interact in production.

SRE teams are often tasked with conducting blameless post-incident reviews that uncover problems in the system. Not focusing on post-incident reviews or not conducting them thoroughly can lead to less reliability and a lack of incident preparedness.

An average day for a site reliability engineer looks like this:

Attending calls to fix/build deployment infrastructure

Ensuring that binaries and configurations are reproducible and applicable for integration deployment environments

Managing configurations of cloud resources for automated deployments

Monitoring software infrastructure, tracking tickets, and checking logs to mitigate risks and resolve existing problems

Participate in sprint planning, code review, code development, and architecture design to foresee risks and offer input on best practices

Plan software deployments with immutable infrastructure using CI/CD

Typical SRE Interview Process

We can break down the entire SRE interview process into a few steps:

Screening: The Company reviews all the applications/resumes received.

Initial Connect: The shortlisted candidates are contacted for an initial conversation about the role over the phone or through video conference to explain the company, job position, and the selection process in detail. It also evaluates the candidate’s motivation, passion, habits and may assess some soft and technical skills. These calls usually last about 30 to 45 minutes. If the applicant fares well, the following technical screen round is set.

Technical Interview: The candidates are called for interviews after the initial conversation. This stage is conducted in two to three rounds, focusing on Unix system internals and coding problems. This phone screen interview round is conducted for 45 to 60 minutes.

On-site Interview: Once you clear the technical interview, they may call you for an on-site interview. This round is organized at the company’s office and may include multiple interviews for various topics, including coding, troubleshooting, Unix system internal, and NALSD. These interviews usually last one and a half hours, and all of them can be done on the same day. This includes separate interviews with the SRE team, manager interviews, and lastly, the director or head of the organization, scoring the candidate against the predefined criteria. Each interview stage has the potential to rule out a candidate.

Offer: After the interviews, all people involved in the recruitment discuss the candidate’s performance and decide whether to extend a job offer. If approved, HR soon notifies the candidate. If the candidate accepts the job offer, the companies will arrange all the job details and inform the starting date. Once you’ve started, the onboarding phase will provide you with all the tools and context necessary to help them tackle challenges!

Tips to Ace the SRE Interview

SRE role has extensive interviews about multiple mediums. Hence the best way to give yourself a chance for the role is to prepare thoroughly. We have compiled some tips to help you ace the interviews.

Practice: Strengthen your fundamentals by practicing coding problems related to data algorithms, architecture, and system design.

Understand the importance of the roles and responsibilities of a Site Reliability Engineer and recollect instances from your experience to share with the interviewers as justification of how you are suitable for the position.

A Site Reliability Engineer applicant must practice as many coding problems related to the data structure, algorithm, and system design as possible. Therefore, strengthening coding fundamentals by practicing is an essential part of SRE interview preparation.

Mock Interviews: Mock Interviews are a great way to deal with on-site stress that might arise at the time of the actual interview. In addition, practicing with colleagues or expert Hiring Managers from the field can help you understand your strengths and weaknesses, thus enhancing your performance during the interview.

Please read about the company, what products and services they offer, and follow their social media handles to keep abreast of the latest developments in the company.

Put your best foot forward by showing your expertise in the technology stack you are more confident in and how you can use it to improve their product/services. Always give some examples/scenarios in support of your views.

If you have relevant experience for the role of SRE, prepare yourself to answer situation-based questions. This is because they will check your strategic behavior, how quickly you can respond to a situation you are not used to, and how you will put your ideas in place to solve a particular problem.

Areas to Focus in an SRE Interview

An SRE interview will involve handling tech-specific questions to hands-on exercises designed to evaluate their skill set and assess their suitability for the role. These questions or tests vary depending upon the organization’s requirements. However, most SRE interviews include major domains, including software development, monitoring and troubleshooting, networking, and infrastructure and operations.

Questions related to Software development are initially asked in the interview to assess the candidate’s knowledge of the programming language and data structures such as queues, stacks, heaps, and algorithms. The hiring manager may ask a candidate to review a poorly written code to identify errors, inefficiencies, and places where the code might fail or produce erroneous results. Other SRE interview questions about software development might involve major applications and interfacing, such as databases.

Monitoring and troubleshooting questions help examine a candidate’s understanding of monitoring principles and practical knowledge of specific tools or practices. For example, the candidate may be asked how they monitor database query times or parse a log file to create a CSV of particular events or processes. They may also be asked questions to gauge their prioritization and time management skills by reviewing a list of monitoring alerts from a tool and rating alerts on priority or severity. Finally, the interviewer may want to assess candidates’ troubleshooting skills. The candidate may be asked to share anecdotal scenarios and actions on specific problems in vital areas such as servers, networks, or services.

Networking questions range from easy to extremely difficult. The hiring manager may initially ask you to explain basic networking concepts such as DNS, Dynamic Host Configuration Protocol, or TCP. However, these questions can become granular, focusing on a specific area that ties up to your experience or study-based questions.

Be prepared for an array of questions on infrastructure and operations. Questions may range from explaining how to secure a container image, the difference between RAID 0 versus RAID 5, and when to use them. Other questions might involve the difference between a service level agreement and service level indicator or between virtualization, containers, and Kubernetes. Infrastructure questions generally become complex and may focus on scalability and IT infrastructure to gauge the candidate’s expertise.

Questions to Expect in an SRE Interview (and How to Answer)

An Interview for the SRE position gives you a chance to showcase your skills and qualification and how you are best suited for the role. While every organization and its SRE department are different, it is ideal for preparing for a few common questions to feel more confident during an SRE interview. SRE interviews often involve workflow and process automation-related questions and require candidates to demonstrate knowledge of prominent IT automation tools. In addition, candidates should be ready to discuss basic automation approaches and practices. Therefore, we have curated a list of essential questions and answers to help you prepare better for an SRE interview.

What’s the Difference Between SRE and DevOps?

While this is more of a generic question, it allows the candidate to highlight the importance of site reliability engineering and showcase your experience in using SRE to bolster resilience and productivity. Some organizations will have dedicated DevOps teams, whereas others follow DevOps methodologies.

A site reliability engineering role focuses on managing the systems belonging to core infrastructure inclined and applicable to the production environment. On the other hand, DevOps is used to inculcate automation and simplification in system development teams and their non-computing parameters. Ultimately, the goal of these two teams is to reduce the gap between development and operations.

What Appeals to You About Becoming a Site Reliability Engineer?

Like any job interview, you need to explain your desire and passion for the SRE role as it is not one of the easiest roles and comes with a lot of responsibilities and pressure. This is an excellent chance for you to display that you are enthusiastic about the role, building services that improve system reliability and lead to greater customer satisfaction. You can explain how being part of an SRE team allows you to make an impact that affects everyone, from product managers to end-users. You can add a couple of experiences you had in a similar role elsewhere and how it was beneficial to the larger organization.

How Does Your Current Deployment Pipeline Look? What Are the Biggest Issues?

This question determines your ability to analyze your deployment pipeline and make intelligent decisions for changing it. You can showcase how in your experience, you, alongside your team, brought significant improvements to resilience without drastically affecting employee productivity to highlight your problem-solving skills.

How Does Your Team Monitor Their System and Track Success?

This question tests the candidate’s knowledge about setting up monitoring and alerting tools and how you’ve helped define a system’s “healthy” state in the past. This is essential as being part of an SRE team; you need to explain how you can leverage internal and external outputs to determine overall system health, translating into actionable insights for the teams.

What Kind of Programming Languages, Tools, and Architecture are You Familiar With?

This is an open-ended question and is asked early in the interview to test your knowledge of different programming languages and technical systems you’ll need to use to do your job. Share the list of tools, programming languages, and architecture you are familiar with, and give instances of how you used it successfully.

How was the Relationship Between your Operations and Engineering Team?

An SRE is involved in multiple aspects of the engineering organization and business; they have a unique perspective on improvement areas. They need to maintain smooth relationships between inter and intra departments and identify bottlenecks in productivity. With this question, the hiring manager is trying to determine how you would work collaboratively with different teams and solve issues between cross-functional teams.

What Does Your On-Call Setup Look Like?

An SRE is responsible for being an on-call efficiency and quality of life steward. Hence for any SRE interview, it’s likely you’ll need to show how you would go about setting up a humane on-call experience. For example, a candidate should explain that on-call should focus more on people when setting up on-call rotations and alert rules instead of processes and tools.

What is observability? Which of the three pillars of observability is most important to you?

Observability measures the system output and analyzes its process’s efficiency, using tools like metrics, logs, and tracing. Generally, SREs are responsible for observability and incident response in the software development life cycle. The three pillars of observability are logging, metrics, and tracing. The interviewee wants to test the candidates’ understanding of observability and how you could help their organization implement this approach.

Can you Explain SLO?

Many people are aware of Service Level Agreement (SLA), but few are aware of Service Level Objective (SLO). An SLA is the uptime promise we make to a customer. These are often legally defined with penalties for missing the target availability. The SLO is a critical element of SLA between the vendor and client agreed beforehand to measure the performance of service providers and is formed as a way of avoiding disputes. SLOs provide a quantitative means to define the level of service a customer can expect from a provider, such as availability, throughput, frequency, response time, or quality. SLA can be understood as a promise to customers for uptime and service availability, while SLO is the goal set to meet the SLA.

SREs are often responsible for developing an SLO and collaborating with multiple teams to ensure realistic and sustainable. Therefore, the candidates should define the SLO and share an example of SLO and how it helps the teams and customers.

Define Service Level Indicators

A Service Level Indicator (SLI) measures the service level provided by a service provider to a customer. SLIs form the basis of SLO, which is a critical element of SLAs. Common SLIs include latency, throughput, availability, and error rate; others include durability, end-to-end latency, and correctness.

SLIs can be measured precisely to define and determine whether you are meeting SLOs and SLAs.

Describe a problem you had to troubleshoot; how did you find it and fix it?

The hiring manager is looking for the candidate’s thinking process and how organized they find problem sources. They also want to check how you can think out of the box in resolving queries.

Here are some additional practice questions you can use to prepare for your SRE interview at Google effectively:

  • What Activities Do You Plan in Your Monthly Maintenance Window?
  • What is an inode?
  • How does a three-way handshake work in TCP?
  • What is the basic memory layout of a process?
  • What are some load-balancing strategies that you can employ?
  • What are the benefits of protocol like QUIC?
  • What are Error Budgets? And for what error budgets are used?

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