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Site Reliability Engineer Interview Questions That Matter

Updated: Jul 31, 2023

10 Site Reliability Engineer Interview Questions That Matter

Site Reliability Engineer Interview Questions And Answers

How would you approach capacity planning for a high-traffic system?

Why is this question asked?

Interviewers ask this question to gauge your understanding of managing resources in a high-traffic environment, and your ability to ensure a system is designed and maintained to withstand unexpected surges.

Example answer:

In my experience, capacity planning for a high-traffic system involves a mix of proactive forecasting, system monitoring, and reactive measures.

It's a strategic process that involves not only understanding the current load but also predicting the future requirements of the system based on business growth, special events, and trends.

First, I conduct an in-depth analysis of the existing system metrics like peak usage times, the average number of requests, and the nature of traffic during those peak times.

I use tools like Prometheus, Grafana, and Google Cloud Monitoring, among others. I analyze these data to understand the current load on our system and to identify any patterns that can indicate how and when the load might increase.

Once I've understood the current state of our system, I do capacity forecasting.

I talk to sales, marketing, and product development to understand our projected business growth, expected product changes, and any specific upcoming events like Black Friday or Cyber Monday that might cause traffic spikes.

This helps me to anticipate changes in system load and prepare for them in advance.

As for infrastructure scalability, I prefer to implement an auto-scaling solution if the technology stack and budget allow.

Auto-scaling, whether vertical or horizontal, can help handle sudden traffic surges while maintaining system stability. For cloud-based solutions, I might use Google Cloud's Auto-scaling or AWS Auto-scaling groups.

Also, I believe in building systems that degrade gracefully. Despite all the planning and auto-scaling, there may still be instances when the traffic exceeds our expectations.

So, we’d plan for such contingencies where some non-critical services might be degraded to maintain the availability and performance of core services.

Finally, I honestly think that capacity planning is not a one-time activity but a continuous process.

So, regular monitoring of the system, updating forecasts as per business changes, and ensuring that the infrastructure scales up and down efficiently are pretty important.

Why is this answer good?

  • The answer demonstrates a thorough understanding of the strategic, analytic, and technical aspects of capacity planning, showing that the candidate can handle the demands of a high-traffic system.

  • The candidate's approach is proactive, collaborative, and adaptable, indicating they can anticipate potential issues, work effectively with different teams, and react quickly to unexpected situations.

  • The response includes specific tools and practices the candidate would use, giving a clear picture of their technical skills and their ability to implement solutions.

  • Lastly, the candidate understands that capacity planning is a continuous process, suggesting they would provide ongoing value to the role.

Can you describe the steps to diagnose a slow server?

Why is this question asked?

This question is important because it tests your problem-solving skills and your ability to diagnose and rectify performance issues efficiently.

The aim is to assess your understanding of system diagnostics and your ability to implement effective solutions.

Example answer:

The first step I usually take is to check the server load.

Tools like 'top' or 'htop' on Linux systems provide a real-time view of the system, showing details about CPU usage, memory usage, and the processes running on the server.

If the CPU or memory utilization is high, it's a clear indication that the server resources are overtaxed. In such cases, identifying and optimizing the processes consuming high resources is necessary.

If the server load seems normal, I move on to check the network.

Tools such as 'ping', 'traceroute', or 'mtr' can be used to diagnose network-related issues. If there are any network latencies or packet losses, they need to be addressed with the network team or the ISP.

In cases where the server load and network appear normal, the next step is to check the application logs. Log files often contain clues about potential issues like exceptions, database queries taking longer time, etc. Tools like ELK Stack or Splunk can be used for log analysis.

If the application logs don't provide any leads, I then look at the database.

Running 'EXPLAIN' on SQL queries can help identify whether the database is properly indexed or whether any query is taking too long to execute. Slow queries need to be optimized, and in some cases, the database schema may need redesigning for efficiency.

In addition to all these, slow disk I/O could also be a reason for a slow server. 'iostat' is a useful tool to check disk I/O statistics.

In some instances, I've found that slow servers can be due to insufficient allocation of resources to the virtual machines, containers, or applications running on the server. So, reviewing the configurations of these components is an essential step as well.

Lastly, if everything else seems fine, it's worth checking for any malware or security breaches that could be causing the server to slow down.

Why is this answer good?

  • The answer is comprehensive and shows a clear process of elimination, demonstrating the candidate's systematic and thorough approach to problem-solving.

  • The use of specific tools and commands demonstrates the candidate's technical skills and ability to practically apply those skills.

  • The candidate's knowledge of both system-level and application-level issues shows their wide-ranging expertise, suggesting they can handle a variety of server-related challenges.

  • The mention of regular monitoring and understanding baseline performance indicates a proactive approach to server management.

Describe a complex distributed system you've worked on. What were the challenges and how did you overcome them?

Why is this question asked?

The interviewer wants to understand your ability to work with complex distributed systems and gauge your problem-solving skills, technical expertise, and experience in overcoming real-world challenges.

The goal is to see how you manage unexpected issues in a live environment.

Example answer:

One of the most complex distributed systems I've worked on was an e-commerce platform that was designed to handle thousands of transactions per second, process large data volumes, and ensure high availability across various geographies.

The system was designed with a microservices architecture, with each service running in a separate Docker container.

All these services were orchestrated using Kubernetes. We used Apache Kafka for event-driven messaging between the microservices. Data was stored in a combination of MySQL for transactional data and Apache Cassandra for large, unstructured data.

One of the main challenges we faced was handling the increased load during peak sales times like Black Friday and Christmas season.

The traffic surge during these periods often caused significant performance issues, leading to slow transaction times and, in worst cases, service unavailability.

To address this, we first implemented an auto-scaling strategy for our Kubernetes pods.

Depending on the CPU usage and the number of incoming requests, new pods would be automatically spawned to handle the increased load, and they would be brought down when the load normalized.

Secondly, we noticed that our MySQL database was becoming a performance bottleneck due to a large number of read/write operations during peak times.

We overcame this by introducing a caching layer using Redis. Frequently accessed data was stored in the cache, thereby reducing the load on our database.

Another significant challenge was ensuring data consistency across various microservices. Due to the nature of distributed systems, network partitions or delays could lead to inconsistent data across different services. To tackle this, we implemented the Saga pattern for distributed transactions, ensuring data consistency even in case of network issues or failures.

Finally, we faced some difficulties in monitoring and troubleshooting the system due to its distributed nature. We addressed this by implementing a centralized logging system using the ELK stack (Elasticsearch, Logstash, Kibana).

This provided us with a unified view of the system and greatly helped in diagnosing and resolving issues quickly.

Why is this answer good?

  • The response is detailed and demonstrates extensive experience with working on complex distributed systems, revealing a deep understanding of their intricacies.

  • The candidate exhibits solid problem-solving abilities, showing how they identified, analyzed, and solved multiple challenges within the system.

  • The use of specific technologies and patterns (Kubernetes, Apache Kafka, MySQL, Apache Cassandra, Redis, Saga pattern, ELK stack) validates the candidate's technical skills and ability to apply them effectively.

  • The answer emphasizes the proactive measures taken to optimize system performance and ensure high availability, demonstrating a commitment to delivering reliable, high-performing systems.

Imagine our website's latency suddenly triples. What steps would you take to identify and address the issue?

Why is this question asked?

The interviewer is trying to evaluate your troubleshooting skills and ability to quickly and efficiently resolve latency issues.

It’s a test of your understanding of the factors that can impact website performance and your competence in using diagnostic tools and techniques.

Example answer:

If a website's latency suddenly triples, it's an indication of a potential issue in several areas: network, server, database, or even the application itself. The steps I would take to diagnose and resolve this issue would be systematic and comprehensive.

First, I'd start by examining the server performance.

I'd look at the CPU, memory, and disk I/O usage using tools like 'top', 'vmstat', or 'iostat'.

If the server is overloaded, it can significantly increase latency. If I identify any resource being heavily used, I would delve deeper into that process, trying to understand why it's consuming so much resource and taking steps to optimize it.

Next, I'd inspect the network. Using tools like 'traceroute', 'ping', or 'mtr', I would check for any network issues that might be causing high latency. This could include problems like packet loss, high network utilization, or network hardware issues.

If network and server performance are both optimal, the next area I'd look into is the application itself. I would check the application logs to identify any errors or bottlenecks.

For web applications, slow web pages could be due to poorly optimized code or large, unoptimized resources like images, CSS, or JavaScript.

At this point, it's also worth examining the database. High latency could be a result of slow database queries. Profiling the database and optimizing slow queries would be part of my troubleshooting process.

If none of the above steps provide a solution, I would consider whether the issue could be related to a sudden increase in traffic.

If that's the case, ensuring that we have proper load balancing and auto-scaling setup can help handle traffic spikes and maintain optimal performance.

Finally, I would not discount the possibility of a DDoS attack. Such an attack could also lead to increased latency, and I would check our security systems to rule this out.

Resolving high latency issues often requires a multi-pronged approach and the ability to look at the system as a whole, rather than just focusing on one aspect.

Why is this answer good?

  • The response provides a systematic and comprehensive approach to diagnosing the problem, demonstrating the candidate's methodical problem-solving skills.

  • The candidate's mention of specific tools and techniques used for troubleshooting shows practical knowledge and technical proficiency.

  • The answer recognizes that the problem can stem from a variety of factors, demonstrating the candidate's understanding of the interconnected nature of web systems.

  • The candidate's awareness of potential security threats like a DDoS attack demonstrates a holistic understanding of system performance and security considerations.

How would you set up monitoring and alerting to ensure maximum uptime?

Why is this question asked?

The interviewer wants to assess your understanding of system monitoring, alerting, and reliability engineering.

Your answer should show your ability to implement preventive measures to ensure system stability, maximum uptime, and timely response to potential issues.

Example answer:

Ultimately, I think the goal is to monitor all critical components of the system and get real-time alerts in case of any anomalies or issues.

To begin, I'd ensure that system-level monitoring is in place.

Tools like Prometheus, Datadog, or Zabbix can monitor metrics like CPU usage, memory usage, disk I/O, and network traffic on all servers. These tools can help identify potential resource constraints that could lead to service disruptions.

Next, I would set up application performance monitoring. Tools like New Relic or AppDynamics can provide crucial insights into how well the application is performing. They can monitor transaction times, database query times, error rates, and other application-specific metrics.

For network monitoring, tools like SolarWinds or Nagios can be used. They can help identify network latency, packet loss, or other network-related issues that could impact service availability.

Given that we live in the age of distributed systems, it's also essential to monitor the health of individual services. For microservices-based architectures, this could mean using service mesh technologies like Istio or Linkerd that provide detailed telemetry data for your services.

Now, having monitoring in place is only half the battle. It's equally crucial to set up intelligent alerting.

Not all anomalies require immediate attention, so it's important to set up alerts based on the severity of the issue. Tools like PagerDuty or Opsgenie can help manage alerts effectively.

Critical alerts that could lead to service disruption should be pushed immediately to the on-call engineer. For less critical alerts, it might be acceptable to send an email or log them for review during regular working hours.

Finally, it's also a good practice to conduct regular reviews of the alerting strategy. This can help identify alert fatigue where too many alerts are being generated, or scenarios where important alerts are missed.

Why is this answer good?

  • The answer shows a comprehensive and multi-layered approach to monitoring and alerting, demonstrating the candidate's understanding of the complexities of system uptime.

  • The use of specific tools for different aspects of monitoring and alerting showcases the candidate's technical expertise and practical experience in this area.

  • The mention of conducting regular reviews of the alerting strategy to avoid alert fatigue indicates the candidate's proactive and long-term approach to system reliability.

  • The acknowledgment of setting up alerts based on the severity of the issue shows the candidate's understanding of the importance of prioritization in incident response.

Can you explain how you would automate a routine maintenance task in our environment?

Why is this question asked?

The aim is to test your skills in automation, a key principle in site reliability engineering to reduce manual intervention, enhance efficiency, and minimize errors.

The interviewer wants to know your ability to use automation tools and scripting languages to streamline routine tasks.

Example answer:

Let's take the example of a routine maintenance task like updating software packages on servers to ensure they are running the latest, secure versions. Automating this task can save a significant amount of time, particularly in a large environment with many servers.

Firstly, I would determine the specific requirements and constraints of the task. This would involve understanding what packages need to be updated, how often, and any potential risks or dependencies that need to be considered.

Next, I would choose an automation tool suitable for our environment. For a Linux-based environment, I might use Ansible because of its agentless nature and ease of use. For a Windows environment, I could use PowerShell DSC (Desired State Configuration).

I would then write a script or playbook that outlines the exact steps that need to be performed. In the case of Ansible, I would define the tasks in a playbook. This playbook would instruct Ansible to check for package updates and apply them.

To ensure that updates are applied consistently across all servers, the playbook would be designed to target all servers in the inventory.

If servers have different roles (e.g., web servers vs. database servers), the playbook could be modified to apply specific updates relevant to each server role.

After the playbook is tested and working as expected, I would schedule it to run at regular intervals using a job scheduler. On Linux, this could be achieved using Cron. On Windows, I could use the Task Scheduler.

Lastly, I'd ensure that the process includes logging and alerting.

This way, if something goes wrong during the update process, I would be notified immediately and can take corrective action. This might involve integrating with a monitoring tool already in use or setting up simple email alerts.

Why is this answer good?

  • The response showcases a systematic approach to task automation, indicating a thorough and methodical mindset.

  • The mention of specific tools and techniques (e.g., Ansible, PowerShell DSC, Cron, Task Scheduler) demonstrates the candidate's technical competency and hands-on experience with automation.

  • The emphasis on logging and alerting shows the candidate's awareness of the importance of feedback and error handling in automation.

  • The consideration of server roles and customizing updates accordingly reveals the candidate's understanding of the complexities and nuances in a real-world environment.

If we were migrating our systems to a new technology stack, how would you ensure a smooth transition and minimal downtime?

Why is this question asked?

This is an important question. The interviewer wants to evaluate your ability to manage complex projects such as technology migrations.

The idea is to explore your strategic planning skills, understanding of risk management, and techniques to minimize downtime during crucial system transitions.

Example answer:

Migrating systems to a new technology stack is a delicate process requiring meticulous planning, effective communication, and careful execution. To ensure a smooth transition with minimal downtime, I would follow a systematic approach.

Firstly, it's vital to understand the scope and goals of the migration. Why are we moving to a new technology stack? What benefits do we expect to see? Understanding the 'why' can inform the 'how'.

Once the objectives are clear, I would conduct an in-depth analysis of the current and target systems. This involves understanding the architecture, data flows, dependencies, potential points of failure, and compatibility between the two systems.

A critical aspect of any migration is designing the migration strategy. This could involve a 'big bang' approach (switching over all at once) or a phased approach (gradually transitioning components or services).

For systems where uptime is critical, I would prefer a phased approach. It allows for easier rollback and reduces the impact of any issues that arise during the transition.

Next, I would prepare a detailed migration plan, outlining each step of the process. This would include a schedule, identifying who is responsible for each task, and defining a rollback plan in case of unexpected issues.

Before the actual migration, I would perform extensive testing. This could involve setting up a mirrored environment and testing the migration process, adjusting the plan as necessary based on the results.

During the migration, I would plan for it to occur during off-peak hours to minimize the impact on users. I would also ensure that effective communication channels are in place to inform all stakeholders about the migration status.

Post-migration, it's essential to thoroughly test the system to ensure everything is functioning as expected. I would also monitor the system closely for any potential issues that may arise.

Finally, learning from the process is crucial. After the migration, I would conduct a retrospective to gather feedback, identify what went well, what didn't, and how we can improve future migrations.

Why is this answer good?

  • The answer demonstrates a structured and methodical approach to managing a technology stack migration, highlighting the candidate's project management skills.

  • The candidate emphasizes risk management strategies such as conducting an in-depth analysis of current and target systems, having a rollback plan, and performing extensive pre-migration testing.

  • The focus on effective communication throughout the process shows the candidate's understanding of its importance in minimizing disruption and ensuring a smooth transition.

  • The inclusion of a post-migration review process illustrates the candidate's commitment to continuous improvement.

Explain how you would handle a security breach in a live environment.

Why is this question asked?

This question is important because it assesses how you would respond to a security incident, an unavoidable risk in modern IT operations.

It evaluates your understanding of incident response procedures, your ability to make quick decisions under pressure, and your grasp of best practices in cybersecurity.

Example answer:

In the event of a security breach, my main goals would be to contain the incident, eliminate the threat, and recover normal operations while minimizing damage.

Firstly, it's crucial to identify and validate the breach.

This could be triggered by an alert from a security monitoring system, a report from an end user, or an abnormality noticed during routine checks. I would gather as much information as possible about the nature of the breach, including what systems or data are affected.

Next, I would work on containing the incident to prevent further damage.

This could involve isolating affected systems or networks, revoking compromised credentials, or blocking malicious IPs at the firewall. It's a balance between preventing further breach and maintaining as much system functionality as possible.

After containment, the next step is eradication, which involves identifying how the attacker breached the system and removing the components used in the attack.

This might involve patching vulnerabilities, removing malware, or changing compromised credentials.

Once the threat is eradicated, I would focus on recovery, ensuring the system is secure before returning to normal operations. This would involve restoring systems from backups, verifying the integrity of data, and validating that all systems are functioning normally.

Throughout the process, it's critical to document everything - actions taken, who performed them, when they were performed, and what the outcomes were. This not only aids in post-incident analysis but is also essential for any legal or compliance requirements.

After the incident, a thorough review should be conducted to understand what happened, why it happened, and how it can be prevented in the future.

This could result in changes to security policies, additional security training for staff, or implementation of new security measures.

Lastly, depending on the nature and severity of the breach, it may be necessary to notify affected parties.

This could include internal stakeholders, customers, or regulatory bodies. It's important to be transparent about what happened, what actions were taken, and how future breaches will be prevented.

Why is this answer good?

  • The answer outlines a structured incident response process, indicating the candidate's understanding of best practices in handling security breaches.

  • The emphasis on documentation and post-incident analysis reveals the candidate's foresight for continuous learning and improvement and awareness of legal and compliance requirements.

  • The consideration of communicating with affected parties shows the candidate's understanding of the broader impacts of a security breach, including reputation and trust.

  • The focus on balancing containment with maintaining functionality reflects the candidate's understanding of the complexities of managing a live security incident.

Can you discuss a time when you implemented a significant infrastructure change? What challenges did you face and how did you address them?

Why is this question asked?

This question provides insights into your practical experience with managing large-scale projects and making major changes in a live infrastructure.

It allows the recruiter to gauge your problem-solving skills, your approach to challenges, and your understanding of risk management.

Example answer:

Certainly, a project that comes to mind involved migrating our company's on-premises servers to a cloud-based infrastructure using AWS. This project was significant due to the scale of the migration and the need to maintain business continuity throughout the process.

The first challenge was the planning stage. We had to ensure that we had a complete understanding of our current infrastructure, including all the services running, the data stored, and the dependencies between services.

We used a variety of tools to map out our system and also held meetings with different teams to fill in any gaps.

Next, we had to ensure that the target cloud environment was adequately configured to host our services. We spent considerable time designing the AWS architecture, keeping scalability, security, and cost-effectiveness in mind.

The actual migration presented the next set of challenges. We decided on a phased approach, moving one service at a time to mitigate risks. This allowed us to resolve any issues without affecting the entire system.

But it also required careful coordination to ensure that the services still on-premises could communicate effectively with those already moved to the cloud.

One specific issue we encountered was with our database migration. Despite careful planning, we experienced some data inconsistencies during the initial migration.

We had to roll back the changes, troubleshoot the issue, and attempt the migration again. The root cause was a minor configuration error that was overlooked in our pre-migration checks, highlighting the importance of thorough testing.

During the migration, communication with stakeholders was crucial. We had to keep everyone informed about the progress, potential downtime, and any issues encountered.

Post-migration, we ran a series of tests to ensure all services were working as expected in the new environment. We also needed to monitor the systems closely for any unforeseen issues.

This project taught me the importance of thorough planning, robust testing, clear communication, and the need to remain adaptable when dealing with complex infrastructure changes

Why is this answer good?

  • The response provides a clear narrative of a complex project, from planning to execution, showcasing the candidate's hands-on experience.

  • It demonstrates the candidate's problem-solving abilities in identifying and overcoming challenges, such as the issue with database migration.

  • The mention of communication with stakeholders reveals an understanding of its importance during significant changes.

  • The candidate's reflection on what they learned from the project indicates their capacity for self-improvement and learning from experience.

Can you describe an incident that required an immediate response from your end? How did you manage and resolve the situation?

Why is this question asked?

The idea is to see if you can react promptly and effectively under pressure.

The interviewer wants to understand your problem-solving skills, knowledge of incident response protocols, and capacity to maintain calm and resolve critical issues when systems fail.

Example answer:

One incident that stands out involved a sudden, unexpected outage in one of our critical production databases. It occurred during peak business hours, making immediate response crucial to mitigate the impact on our customers and business operations.

As soon as I received the alert, I began troubleshooting the issue. By checking the system logs, I identified that the database server was unresponsive due to an unusually high load.

To address this immediate concern, I first scaled up the server resources to handle the increased load and restarted the database service, which brought the system back online.

After ensuring the immediate restoration of the service, my next goal was to understand why this unexpected load had occurred to prevent a recurrence.

On inspecting the logs and traffic patterns, I discovered a poorly optimized query that was causing a full table scan on a large database table, causing the server to exhaust its resources.

I collaborated with the development team to optimize the query, reducing the system load significantly. We tested the updated query thoroughly in a non-production environment before deploying it to the production database.

In addition, to avoid future disruptions due to similar issues, I implemented more granular monitoring for database load, enabling earlier detection of any unusual patterns.

I also proposed a review of our database queries as part of our regular code reviews to catch potential issues earlier.

Finally, I documented the incident, the investigation process, and the steps taken to resolve it. This was important not only for record-keeping but also as a learning resource for the team to handle similar situations in the future.

Why is this answer good?

  • The candidate shows a structured approach to incident management, demonstrating their ability to respond efficiently under pressure.

  • The answer highlights their problem-solving skills and their collaboration with other teams to find and implement a solution.

  • The candidate's emphasis on proactive measures and learning from the incident demonstrates their commitment to continuous improvement.

  • By documenting the incident, they illustrate an understanding of the importance of knowledge sharing and learning within the team.


There you have it — 10 Important Site Reliability Engineer interview questions and answers. Now, the reason we’ve gone with just ten questions is twofold — one, no one’s going to ask you a hundred simple questions. That’s not how interviews work.

Second, we’ve actually answered quite a few simpler, smaller questions within these larger, more elaborate answers. This way, you won’t end up reading the same thing again and again.

Use this blog as a guide and we’re sure great jobs won’t be too far away.

On that front, if you’re looking for remote Site Reliability Engineer jobs, check out Simple Job Listings. We only list verified, fully remote jobs that pay well. For context, the average salary for Site Reliability Engineers on our job board is $140,750.

Visit Simple Job Listings and find amazing remote Site Reliability Engineer roles. Good luck!



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