Interview Practice & Self-Assessment

~20 min · Final Lesson · Hello Interview · Exponent

Ref

Primary Source

Hello Interview & Exponent SRE System Design Evaluation Frameworks

The definitive guide to FAANG evaluation rubrics, handling design curveballs, and structured mock execution.

The 45-Minute Interview Checklist

A system design interview is not a test of your ability to memorize architectures. It is a **collaborative design session**. The interviewer wants to see how you think, communicate, and navigate trade-offs. Remember the golden breakdown:

Time Breakdown (45 Mins)

• Step 1: Understand & Scope (5-7 Mins): Functional/Non-functional requirements.
• Step 2: Estimation (5 Mins): QPS, storage, bandwidth back-of-the-envelope calculations.
• Step 3: High-Level Design (10-15 Mins): Draw API endpoints, database schema, block diagrams.
• Step 4: Deep Dive (15 Mins): Scale bottlenecks, caching, failure cases, concurrency control.

Common Interview Pitfalls

Pitfall	Why it Hurts You	How to Avoid
Silence	Interviewer cannot evaluate your thoughts.	Talk continuously. Treat it as a pair programming exercise. Say: "I am thinking of using Redis here because..."
Rabbit Holes	Spending 20 minutes explaining database schema details, running out of time for scaling.	Keep a high-level view first. Ask: "Should we deep dive into the upload chunking details, or would you like to review database partitions?"
No Trade-offs	Proposing one solution as "perfect". Suggests lack of production experience.	Always present options. Say: "We could use standard replication for simplicity, but a masterless quorum gives us higher write availability."
Ignoring Scope	Designing a global Netflix system when you were only asked for a simple video upload queue.	Tie every component back to the requirements established in Step 1.

Handling Interview Curveballs

Midway through, the interviewer might change parameters: "What if the database master server explodes? What if we have a sudden 100x traffic spike because of a viral event?"

Don't panic: Curveballs are a good sign. It means you finished the core design quickly.
Acknowledge the bottleneck: "Yes, that creates a write bottleneck. Let's look at sharding the tables."
Reach for your toolbox:
• For database crashes → replication replica failover, multi-region setups.
• For traffic spikes → queues (backpressure), caching, rate limiters, CDN offloading.
• For data conflicts → vector clocks, quorum checks, client merge policies.

Final Course Self-Assessment

1. During a system design interview, what is the single most important element to evaluate and vocalize when choosing a component?

2. When asked to scale a system to handle a massive traffic spike, what is the best first design recommendation?

3. How should you structure your collaboration with the interviewer during the design phase?