Engineering Ic interview prep.

Behavioural questions to expect

1. Walk me through your CV.
2. Tell me about your most impactful technical project.
3. Tell me about a weakness, a failure, or feedback you've received and worked on.
4. Why consumer internet engineering - and why the firm specifically vs enterprise SaaS or infra?
5. Which team or technical area would you want to work on, and why?
6. Why the firm?
7. How would you describe the firm's engineering organisation + architecture in your own words?
8. How does engineering actually drive value at a consumer-internet firm?

Technical concepts to master

• CAP + consistency at consumer scale

  CAP at consumer scale · Eventual consistency + read-your-writes · Fan-out on write vs read · Idempotency at scale

• Sharding + replication + hot keys (consumer)

  Sharding by user / content · The celebrity / hot-key problem · Multi-region + edge serving · Cache + invalidation at consumer scale

• A/B testing + growth engineering

  A/B platform architecture · Sample size + statistical power · Primary + guardrail metrics · Growth funnel + experimentation

• Observability + golden signals (consumer)

  The four golden signals · Business funnel + metric instrumentation · SLI / SLO / error budget · Blast radius + canary / staged rollout

Practical drills

• A consumer feed service has 500M DAU. Each user opens the app 5x / day on average; each feed request returns 20 items + rendering takes 1MB of media. P99 latency target 300ms. (a) Average + peak QPS. (b) Daily bandwidth. (c) Storage (assume each item is 500B + media is CDN-cached). (d) Rough estimate of feed-serving infrastructure (servers, cache, CDN).
• Design a personalized recommendation feed for the firm's consumer app at 200M DAU. Walk me through it.
• the firm's DAU has dropped 3% over the last 48 hours, primarily in mobile. Walk me through how you'd diagnose + fix.

Smart-question anchors

• Team + scope - the team's surface area, what the role would specifically own in 6-12 months
• Stack + architecture - the current stack, recent architecture changes, where the eng team thinks it's heading
• A/B + experimentation culture - cadence, platform, OKR integration, how decisions are made on experiments
• On-call + reliability - on-call rotation, SLO + error-budget approach, recent incident learnings
• Career ladder + growth - what differentiates Mid / Senior / Staff at this firm, mentoring, IC track

Sourced from

interviewing.io — Senior Engineer's Guide to System Design · IGotAnOffer — System Design Interview Questions & Prep (FAANG) · Hello Interview — System Design in a Hurry (CAP, consistency, design patterns) · Tech Interview Handbook — Behavioral Interview Questions for SWE · Google SRE Book — The Four Golden Signals + observability canon · Hello Interview + Newsletter Eng-Leadership — A/B testing + growth engineering