Contrast Security India Site Reliability Engineer Interview: Rounds, Questions and Preparation

What the job involves

Site Reliability Engineers (SREs) at global tech companies like Contrast Security India ensure that production systems are reliable, scalable, and efficient. Day to day, they monitor services, respond to incidents, automate repetitive tasks, and improve system resilience through code and infrastructure changes. Freshers in this role typically start with incident triage, writing automation scripts, and learning observability tools.

Role and Technical Knowledge

1. 1

   What is the difference between a Site Reliability Engineer and a DevOps Engineer?

   Highlight that SRE applies software engineering to operations, with a focus on reliability, SLIs/SLOs, and error budgets, while DevOps is a broader cultural and process movement.

2. 2

   Explain the concept of an error budget and how you would use it.

   Define error budget as 1 minus SLO, and explain how it balances innovation and reliability; mention using it to decide when to freeze releases or invest in reliability.

3. 3

   What are SLIs, SLOs, and SLAs? Give an example for a web service.

   SLI is a metric (e.g., latency), SLO is a target (e.g., 99.9% of requests under 200ms), SLA is a contract with consequences. Use a concrete web service example.

4. 4

   How would you approach capacity planning for a service that is growing 20% month over month?

   Mention monitoring trends, forecasting, load testing, and scaling strategies (horizontal vs vertical), and include a buffer for spikes.

Practical Scenarios

1. 5

   A production server is running out of disk space. How do you troubleshoot and resolve it?

   Walk through checking disk usage with df and du, identifying large files or logs, rotating logs, cleaning up, and setting up alerts to prevent recurrence.

2. 6

   Users report that your website is slow. How do you diagnose the issue?

   Start with monitoring dashboards (latency, error rates), check server metrics (CPU, memory, I/O), network latency, and database queries; use tracing to pinpoint bottlenecks.

3. 7

   You need to deploy a new version of an application with zero downtime. What strategy would you use?

   Discuss blue-green deployments or canary releases, health checks, rollback plans, and load balancer configuration.

4. 8

   How would you automate the process of restarting a failed service?

   Mention writing a script or using a supervisor like systemd, or orchestration tools like Kubernetes liveness probes, and adding alerting for failures.

Behavioural and HR

1. 9

   Tell me about a time you had to learn a new technology quickly for a project.

   Use STAR method: describe the situation, the technology, how you learned it (online resources, documentation, peers), and the positive outcome.

2. 10

   Describe a situation where you worked under pressure or with a tight deadline.

   Show how you prioritized tasks, communicated with the team, and remained calm; highlight the result and what you learned.

3. 11

   How do you handle a disagreement with a teammate about a technical solution?

   Emphasize listening, data-driven discussion, and focusing on the best outcome for the project; mention compromise or escalation if needed.

4. 12

   Why do you want to work as an SRE, and why our company?

   Connect your interest in reliability and automation to the company's mission and tech stack; show you have researched the company's products and culture.

Coding and Automation

1. 13

   Write a Python script to check if a given URL is reachable and return its HTTP status code.

   Use requests library, handle exceptions, and print status; mention timeout and error handling.

2. 14

   How would you parse a log file to count the number of 500 errors per hour?

   Use grep, awk, or Python to filter lines with 500 and group by hour; discuss efficiency for large files.

3. 15

   Given a list of server names, write a script to SSH into each and check disk usage.

   Use Python with paramiko or subprocess, loop through servers, run df -h, and collect output; mention error handling for unreachable hosts.

4. 16

   Explain how you would use a configuration management tool like Ansible to ensure a service is running.

   Describe writing a playbook with tasks to install, configure, and start the service, and using handlers for restarts; mention idempotency.