Top Site Reliability Engineer Interview Questions & Answers (2026)

💬 Can you explain the difference between an SLA, SLO, and SLI?

Why they ask: To verify your understanding of foundational SRE concepts and how they relate to measuring and maintaining system reliability.

Sample answer: An SLI, or Service Level Indicator, is a direct measurement of a service's behavior, like request latency or error rate. An SLO, or Service Level Objective, is the target value or range of values for a service level that is measured by an SLI, such as aiming for 99.9% availability. An SLA, or Service Level Agreement, is an explicit or implicit contract with your users that includes consequences of meeting or missing the SLOs. In my previous role, I helped define our SLOs based on critical user journeys, ensuring our engineering teams were aligned on reliability targets.

💬 How do you handle a high-severity production incident?

Why they ask: To assess your incident management skills, ability to remain calm under pressure, and systematic approach to troubleshooting.

Sample answer: During a high-severity incident, my first priority is to stop the bleeding and mitigate the impact on users, often by rolling back a recent deployment or scaling up resources. Once the system is stabilized, I take on or assign the Incident Commander role to coordinate communication and investigation. After resolving the root cause, I always lead a blameless post-mortem to identify systemic vulnerabilities and implement action items that prevent the issue from recurring. For instance, when our payment gateway went down, I quickly rerouted traffic to a fallback provider before investigating the underlying database deadlock.

💬 Describe your approach to capacity planning.

Why they ask: To evaluate your ability to forecast resource needs and ensure systems can handle future growth without over-provisioning.

Sample answer: I approach capacity planning by analyzing historical metrics for CPU, memory, and network usage to identify growth trends and seasonal spikes. I then correlate these trends with upcoming product launches or marketing campaigns to forecast future demand. To ensure we have enough headroom, I establish load testing procedures to determine the breaking point of our current architecture. At my last company, this proactive approach allowed us to seamlessly handle a 300% surge in traffic during Black Friday by pre-scaling our Kubernetes clusters.

💬 What is Error Budget, and how do you use it?

Why they ask: To see if you understand how to balance the need for system stability with the desire for rapid feature development.

Sample answer: An Error Budget is the allowable threshold for unreliability, calculated as 100% minus the SLO. It provides a clear, objective metric to balance feature velocity and system stability. If a service is within its error budget, developers can push new features rapidly; if the budget is depleted, the focus must shift entirely to reliability tasks until the budget recovers. I once used our depleted error budget to justify a two-week feature freeze, allowing the team to refactor a brittle microservice and ultimately improve our long-term availability.

💬 How do you implement Infrastructure as Code (IaC)?

Why they ask: To check your practical experience with automation tools and your ability to manage infrastructure through version-controlled code.

Sample answer: I strongly advocate for managing all infrastructure through IaC tools like Terraform or AWS CloudFormation, treating infrastructure changes with the same rigor as application code. I ensure all IaC is version-controlled in Git, requires peer review, and is deployed via a CI/CD pipeline to maintain consistency across environments. Recently, I migrated our manual AWS provisioning to Terraform, which reduced our environment setup time from days to minutes and eliminated configuration drift.

🧠 Tell me about a time you had to push back on a development team regarding a release.

Tip: Focus on your communication skills, empathy, and how you used data (like SLOs or error budgets) to justify your decision objectively.

🧠 Describe a situation where you had to learn a new technology quickly to solve a problem.

Tip: Highlight your adaptability, continuous learning mindset, and the specific steps you took to master the new tool.

🧠 Can you share an example of a time you automated a tedious, repetitive task?

Tip: Explain the pain point, the automation solution you designed, and the measurable time or resources saved.

🧠 How do you handle disagreements with team members during a post-mortem?

Tip: Emphasize your commitment to a 'blameless' culture, focusing on systemic failures rather than individual mistakes.

🧠 Tell me about a time you failed to meet an SLO. What happened and what did you learn?

Tip: Be honest about the failure, focus on the root cause analysis, and detail the actionable steps taken to prevent a recurrence.

🔧 How would you design a highly available, fault-tolerant web architecture?

Tip: Discuss load balancing, multi-region deployments, database replication, caching strategies, and auto-scaling.

🔧 Explain how a Linux system boots up, from pressing the power button to the login prompt.

Tip: Cover the BIOS/UEFI, MBR/GPT, GRUB/Bootloader, Kernel initialization, and the init system (like systemd).

🔧 What happens when you type 'google.com' into your browser and press Enter?

Tip: Walk through DNS resolution, TCP handshake, TLS negotiation, HTTP request/response, and browser rendering.

🔧 How do you troubleshoot a process that is consuming 100% CPU on a Linux server?

Tip: Mention tools like top, htop, strace, perf, and how you would analyze the process's system calls and stack traces.

🔧 Describe the architecture of Kubernetes and the role of its core components.

Tip: Explain the Control Plane (API server, etcd, scheduler, controller manager) and the Worker Nodes (kubelet, kube-proxy, container runtime).