DevOps Interview Prep (FAANG)

A Senior DevOps Engineer at FAANG earns $250-450K/year. The difference between junior and senior in an interview is not knowing more commands - it is the ability to reason about systems under uncertainty and communicate tradeoffs demonstrably. This is a learnable skill.

• **Google L5 SRE** typical questions: 'How would you detect that your service is starting to degrade 5 minutes before a full outage?' - testing understanding of SLI/SLO and alerting strategy.
• **Amazon Principal Engineer** system design: 'Design a deploy pipeline for 10,000 microservices with zero-downtime requirements' - expecting cell-based deployment and canary strategy.
• **Meta Staff Engineer** outage question: '100M users cannot log in. You have 15 minutes. What do you do?' - evaluating systematic troubleshooting, communication, and prioritization.

Design CI/CD Pipeline

Typical FAANG question: 'Design a CI/CD pipeline for a microservice with 100 engineers'. Expected structure: clarifying questions first, then pipeline stages with justification, then rollback strategy, database migrations, secrets, and canary deployment.

FAANG interviewers evaluate the process: did the candidate ask clarifying questions before diving into the solution? A candidate who immediately describes a specific stack (GitHub Actions + ArgoCD + Helm) without asking about the context scores lower than one who gathers requirements first.

Troubleshoot Production Outage

Question: 'Production API returned 500 errors for 5 minutes. What do you do?' Structure: Detect - Triage - Mitigate - Root Cause - Postmortem. Key principle: mitigation is primary, root cause is secondary.

FAANG interviews reward systematic approach over specific tool knowledge. An engineer who says 'first I check Kibana logs, then Jaeger traces, then deployment history' demonstrates the right mental model regardless of which specific tools are named.

Capacity Planning

Capacity planning determines resources needed to handle expected load with headroom. FAANG interviews expect: baseline measurement, peak estimation with safety factor, and cost/performance tradeoff awareness.

Capacity planning interviews test numerical reasoning, not memorized formulas. State assumptions explicitly: 'I am assuming linear scaling - if caching hit rate drops at peak, actual capacity needed may be higher.'

Architectural Tradeoffs

FAANG DevOps interviews test the ability to justify tradeoffs between alternatives. There is no single 'correct' answer - the correct answer is: describe both options with context-specific justification, and name what is sacrificed in the chosen approach.

Tradeoff questions have no correct answer key. Interviewers at Meta, Google, and Stripe evaluate reasoning quality: 'Given these constraints (high write throughput, global distribution, eventual consistency acceptable), DynamoDB fits better than PostgreSQL because...' This framing demonstrates senior-level thinking.

Summary

• **CI/CD Design** - start with requirements (not tools); describe pipeline stages with justification; key topics: rollback strategy, DB migrations, secrets, canary deployment.
• **Troubleshoot Outage** - mitigation first, root cause second; structure: Detect - Triage - Mitigate - Root Cause - Postmortem; demonstrate systematic approach.
• **Capacity + Tradeoffs** - calculate server count with safety factor and target utilization; tradeoff questions require describing both options with context, not naming a winner.

Related Topics

Interview preparation builds on the full DevOps knowledge stack:

• Reliability Engineering at Scale — Cell architecture, blast radius, and chaos engineering are typical senior DevOps design questions at FAANG.
• On-Call and Incident Management — The troubleshoot outage question tests understanding of incident response process and postmortem culture.

Вопросы для размышления

• How do you explain the choice of Kubernetes vs Lambda for image processing at 1,000 uploads/day vs 1M uploads/day?
• Capacity planning: what metrics are needed to answer 'how many servers do we need next year'?
• If the interviewer says 'your answer is wrong' on a tradeoff question - how do you correctly respond?

Связанные уроки

• os-23-interview-patterns