How to Win Your System Design Interview: Start Simple, Score Big

The architecture that gets you hired (and actually works in production)

i had my fair share of experiences with system design interviews to know that getting a quick win is a huuge plus in the eyes of the interviewer and a confidence boost for yourself.

starting with Kubernetes, microservices, and event-driven architectures for a basic CRUD application is redundant, but many people do it and get lost during their explanations...

you know what can get you a few steps closer to getting hired? starting with this:

let me show you why this "boring" approach will help you nail your next system design interview - and why it's what actually powers most successful companies.

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The Interview Strategy That Works

Start With What Actually Runs in Production

When your interviewer asks you to "Design Instagram" or "Build a URL shortener," resist the urge to impress with complexity.

here's the reality: Instagram scaled to 14 million users with Django and PostgreSQL. GitHub still runs on a Ruby on Rails monolith with over 1,000 engineers collaborating daily. Stack Overflow handles 6000+ requests per second with just 9 servers running a monolithic architecture.

your interviewer knows this. they want to see if you do too.

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The Winning Foundation

start every system design with these components:

1. API Gateway

• authentication & authorization

• rate limiting

• request routing

• SSL termination

Interview tip: mention this shows you understand security and traffic management from day one.

2. Backend Service (Your Monolith)

• business logic in one deployable unit

• stateless for easy horizontal scaling

• single codebase = faster iteration

Interview tip: Give an example, like how Instagram's Django monolith allowed them to deploy code in seconds using Fabric.

3. PostgreSQL

• ACID compliance for data integrity

• Complex queries with JOIN support

• JSONB for flexible schemas

• Extensions for specialized needs (PostGIS, pg_vector)

Interview tip: Modern PostgreSQL with AWS RDS can handle millions of rows and thousands of connections. It's not your bottleneck.

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Why This Impresses Interviewers?

✔️ you understand constraints

good engineers know that complexity has a cost:

• every service boundary is a network call

• every network call can fail

• every failure needs handling

• every handler adds complexity

When you start simple, you show you understand these trade-offs.

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✔️ you can scale.. when needed

here's how to discuss scaling in your interview (Claude Generated examples - very valid!) 👇

Phase 1: Vertical Scaling (0-100K users)

"We'll start with vertical scaling. Modern servers with 64GB RAM can handle thousands of requests per second. Stack Overflow proves this works at scale."

Phase 2: Read Replicas (100K-1M users)

"When reads overwhelm writes, we add PostgreSQL read replicas. Instagram used this pattern successfully with master-replica architecture."

Phase 3: Caching Layer (1M+ users)

"We'll add Redis/Memcached for hot data. Instagram used Memcached for general caching and Redis for feeds."

Phase 4: Service Extraction (When Actually Needed)

"Only when we have clear domain boundaries and separate teams, we'll extract services. GitHub only recently started extracting services from their monolith after years of success."

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✔️ you know the numbers

some facts you can drop in your interview ⭐️

• PostgreSQL with proper indexing can handle tens of thousands of requests with light caching

• Stack Overflow's monolithic SQL Server handles over 10,000 queries/second at ~15% CPU

• Instagram's PostgreSQL connections were pooled using Pgbouncer for massive performance gains

• a single Redis instance can handle 60,000+ ops/s

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Bonus: Some Red Flags 🚩 to Avoid

just don't say:

• "Microservices are always better"

• "SQL doesn't scale"

• "Monoliths are legacy"

• "We need Kubernetes from day one"

these statements show inexperience and trend-following rather than engineering judgment.

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Your Interview Checklist

✅ Start with the simple architecture
✅ Explain why it works (with real examples)
✅ Show how to scale incrementally
✅ Address concerns proactively
✅ Use concrete numbers and examples
✅ Demonstrate trade-off thinking
✅ Keep complexity as the last resort

Start simple. Scale when needed. Get the job.

and more thing..

don’t just memorize this diagram and draw it on the whiteboard. Learn each component in-depth. Be prepared to answer any question regarding it and how it can be extended, utilized, optimized..

learn the scenarios where this design isn’t actually enough

otherwise, you will end up like:

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found this helpful?

forward it to someone preparing for system design interviews. They'll thank you when they get the offer! ❤️