Introduction
Site Reliability Engineering (SRE) is one of the most critical and sought-after roles in 2025. Companies like Google, Amazon, and Microsoft are looking for engineers who can bridge the gap between software development and IT operations while ensuring reliability, scalability, and performance of critical systems.
This guide provides the Top 25 Site Reliability Engineer (SRE) Interview Questions and Answers, including detailed explanations, real-world examples, and best practices to help you succeed in SRE interviews.
Top 25 Site Reliability Engineer (SRE) Interview Questions and Answers
1. What is Site Reliability Engineering (SRE)?
Answer:
SRE is a discipline that incorporates software engineering practices into IT operations to ensure reliable and scalable systems. SRE focuses on automation, monitoring, incident response, and improving system reliability, often using software to manage infrastructure efficiently.
Example: Automating server provisioning, monitoring services, and creating dashboards to track system health.
2. Explain the key responsibilities of an SRE.
Answer:
Monitoring and maintaining production systems
Incident response and postmortem analysis
Capacity planning and scaling infrastructure
Implementing automation to reduce manual work
Defining Service Level Objectives (SLOs) and Service Level Indicators (SLIs)
Ensuring fault tolerance, reliability, and performance
3. What is the difference between SRE and traditional DevOps?
Answer:
DevOps focuses on collaboration between development and operations teams to deliver software quickly.
SRE emphasizes reliability, using engineering solutions to prevent manual operational work, often measuring success through SLOs and error budgets.
4. What are SLIs, SLOs, and SLAs? Explain the difference.
Answer:
SLI (Service Level Indicator): Metric that measures a system’s performance (e.g., request latency, error rate).
SLO (Service Level Objective): Target value for SLIs (e.g., 99.9% uptime).
SLA (Service Level Agreement): Contractual agreement with customers specifying reliability guarantees.
Example:
SLI = % of HTTP requests served successfully
SLO = 99.95% success rate
SLA = Promise to customers for 99.9% uptime
5. What is an error budget, and how is it used?
Answer:
An error budget represents the acceptable threshold of system errors or downtime based on the SLO. Teams use it to balance innovation vs. reliability.
Example: If SLO is 99.9% uptime, the error budget is 0.1%. Teams can deploy risky features as long as the error budget isn’t exhausted.
6. How do you approach incident management?
Answer:
Detection: Monitor alerts and SLIs
Response: Triage, mitigate, and restore service
Communication: Notify stakeholders
Root Cause Analysis (RCA): Identify the cause
Postmortem: Document findings, lessons learned, and preventive actions
7. What is chaos engineering?
Answer:
Chaos engineering involves deliberately introducing failures to test system resilience. This helps identify weak points before they cause real outages.
Example: Netflix Chaos Monkey randomly terminates servers in production to test redundancy.
8. What are common monitoring tools for SREs?
Answer:
Prometheus
Grafana
Nagios
Datadog
ELK Stack (Elasticsearch, Logstash, Kibana)
Splunk
Monitoring focuses on metrics like latency, error rates, traffic, saturation, and system health.
9. How do you handle high latency or performance degradation in production?
Answer:
Identify the source (CPU, memory, network, database)
Scale horizontally or vertically
Optimize queries and caching
Rate limiting and throttling requests
Implement circuit breakers and retries
10. What is load balancing, and why is it important?
Answer:
Load balancing distributes traffic across servers to improve availability and reduce latency. Techniques include round-robin, least connections, IP hash, and weighted balancing.
11. What is the difference between vertical and horizontal scaling?
Answer:
Vertical Scaling: Increasing resources (CPU, RAM) of a single server
Horizontal Scaling: Adding more servers to handle increased load
Horizontal scaling is often preferred for high availability and fault tolerance.
12. How do you ensure high availability in a distributed system?
Answer:
Deploy services across multiple regions/zones
Use replication and redundancy
Implement failover mechanisms
Monitor system health with automated alerts
Use load balancers and caching strategies
13. What is a rolling update?
Answer:
Rolling updates deploy new versions gradually across servers, minimizing downtime and reducing risk. If an issue occurs, it can be rolled back.
14. Explain canary deployments.
Answer:
Canary deployments release new features to a small subset of users first, monitoring impact before a full rollout. Helps mitigate risk of new code.
15. How do you manage configuration changes in production?
Answer:
Use version control (Git) for configuration
Automate deployment with CI/CD pipelines
Test changes in staging environments
Rollback safely if needed
16. What is infrastructure as code (IaC)?
Answer:
IaC is managing infrastructure using code instead of manual processes. Tools include Terraform, Ansible, CloudFormation.
Benefits: Automation, consistency, scalability, repeatability.
17. How do you perform capacity planning?
Answer:
Analyze historical traffic data
Predict growth trends
Plan resources for peak loads
Factor in redundancy and failover
Adjust SLOs if necessary
18. What is disaster recovery, and what strategies do you use?
Answer:
Disaster recovery ensures systems recover quickly after outages. Strategies:
Backup & restore
Active-active multi-region deployment
Hot/cold standby systems
Regular DR drills
19. What is a postmortem, and why is it important?
Answer:
A postmortem documents what went wrong, why, and how to prevent recurrence. Key points: timeline, impact, root cause, and actionable lessons.
Example: Google SRE postmortem culture emphasizes blameless analysis.
20. How do you handle alert fatigue?
Answer:
Tune alert thresholds
Reduce false positives
Use aggregated alerts
Categorize alerts by severity
Implement automated remediation when possible
21. How do you implement fault tolerance in cloud systems?
Answer:
Replicate services across regions
Use redundant databases
Implement retry and fallback mechanisms
Monitor and auto-heal failed instances
22. Explain the difference between scaling stateless vs stateful applications.
Answer:
Stateless: No client data stored locally; easy to scale horizontally
Stateful: Maintains state; requires careful replication and data consistency strategies
23. What is SLO-based alerting?
Answer:
Alerts are triggered only when SLOs are breached, reducing noise and focusing on user-impacting issues.
Example: Error rate exceeds 0.1% → alert.
24. How do you manage deployments in microservices architectures?
Answer:
Use CI/CD pipelines
Canary/Blue-Green deployment
Monitor inter-service communication
Handle versioning and backward compatibility
25. How do you prepare for SRE interviews?
Answer:
Master Linux, networking, and cloud concepts
Understand DevOps tools (Terraform, Jenkins, Kubernetes)
Learn monitoring and incident management best practices
Prepare examples of automation, reliability improvements, and postmortems
Practice scenario-based questions
Conclusion
Site Reliability Engineering combines software engineering, operations, and reliability best practices to maintain high-performing systems. By mastering these 25 detailed SRE interview questions, you’ll be prepared for high-level technical interviews at companies like Google, Amazon, and Microsoft.
Focus on real-world examples, automation experience, and incident handling scenarios to stand out.