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 SaaS enterprise engineering - and why the firm's segment vs consumer internet 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 and architecture in your own words?
8. How does engineering actually drive value at a SaaS firm like the firm?

Technical concepts to master

• CAP theorem + consistency models

  CAP - the framing · Strong vs eventual consistency · ACID vs BASE · Idempotency + at-least-once semantics

• Sharding + replication

  Sharding (horizontal partitioning) · Hot key / hot tenant problem · Replication - sync vs async, leader vs leaderless · Multi-region + replication lag

• Caching + invalidation

  Cache strategies (write-through, write-back, write-around) · Cache invalidation - TTL, explicit purge, event-driven · Thundering herd + cache stampede · CDN + edge caching

• Observability + the four golden signals

  The four golden signals · Metrics + logs + traces - the three pillars · SLI / SLO / error budget · Blast radius + change-management

Practical drills

• A SaaS firm's primary write API receives 50M write requests / day from 100K tenants, average payload 2KB, with a target P99 latency of 300ms and 99.95% availability. (a) Average + peak QPS. (b) Daily + annual storage growth. (c) Rough QPS the read replica needs if reads are 10x writes. (d) How many app servers (assume ~500 QPS / server for a write-heavy workload)?
• Design a multi-tenant API rate limiter for the firm's public API. Tenants have plans (Free, Pro, Enterprise) with different limits. Walk me through it.
• A service that runs at P99 of 200ms is suddenly at 800ms; P50 is unchanged. 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
• Code culture - code review, RFC / design-doc discipline, deploy cadence, release process
• On-call + reliability - on-call rotation, SLO + error-budget approach, recent incident learnings, postmortem culture
• Career ladder + growth - what differentiates Mid from Senior from Staff at this firm, mentoring, technical IC track vs management

Sourced from

interviewing.io — Senior Engineer's Guide to the System Design Interview · IGotAnOffer — System Design Interview Questions & Prep (from FAANG experts) · Hello Interview — System Design in a Hurry (CAP, consistency, design patterns) · Tech Interview Handbook — Behavioral Interview Questions for Software Engineers · Eng Leadership Newsletter — Big Tech Behavioral Interviews for Senior SWE · Google SRE Book — The Four Golden Signals + observability canon