How to practice for a system design interview?

The best way to practice system design is by simulating real-world architectures. MockArch provides an interactive system design simulator where you can construct cloud architectures, simulate real-time traffic, estimate infrastructure costs, and on Pro get LLM deep analysis on your design choices.

How does MockArch AI feedback work?

On Pro, deep LLM analysis evaluates your design for bottlenecks, scaling issues, and security, with a monthly usage cap per subscriber (quota resets at 00:00 UTC on the first day of each calendar month). You receive concrete recommendations for improvements. Free tier includes automated rule-based checks.

Can I cancel my MockArch Pro subscription anytime?

Yes. The Pro tier is billed month-to-month with no long term contracts. You will retain access to Pro features until the end of your billing cycle.

How is MockArch different from Miro or Excalidraw?

Those are general diagram tools. MockArch is built for system design interview prep: you get real-time cost estimates, load simulation, and on Pro, LLM feedback that suggests expert improvements. Interview scenarios and scoring are available on free tier for easy difficulty; medium and hard scenarios require Pro.

What are the core concepts of system design?

Core concepts include scalability (horizontal vs vertical), load balancing, caching strategies, database sharding, CAP theorem, and microservices architecture. MockArch helps you practice and visualize all these components interactively.

How to choose between SQL and NoSQL in a system design interview?

Choose SQL for structured data with complex relationships and ACID compliance requirements. Choose NoSQL for unstructured data, horizontal scalability, and rapid schema iteration. Use MockArch's simulator to compare the performance and cost tradeoffs of both.

How do load balancers work in system architecture?

Load balancers distribute incoming network traffic across multiple servers to ensure no single server bears too much demand, improving responsiveness and availability. In MockArch, you can drag and drop load balancers to see how they impact your system's bottleneck limits.

What is the best way to prepare for FAANG system design interviews?

The most effective preparation combines reading foundational texts (like Designing Data-Intensive Applications), practicing whiteboard problems, and using interactive simulators like MockArch. Pro includes deep LLM analysis to complement your practice; the free tier includes rule-based checks and simulation.

Can I estimate AWS cloud infrastructure costs?

Yes. MockArch acts as a dynamic infrastructure cost calculator. As you add databases, compute instances, and define traffic volumes, the simulator provides a real-time estimation of your monthly cloud spend.

How to practice for a system design interview?

The best way to practice system design is by simulating real-world architectures. MockArch provides an interactive system design simulator where you can construct cloud architectures, simulate real-time traffic, estimate infrastructure costs, and on Pro get LLM deep analysis on your design choices.

How does MockArch AI feedback work?

On Pro, deep LLM analysis evaluates your design for bottlenecks, scaling issues, and security, with a monthly usage cap per subscriber (quota resets at 00:00 UTC on the first day of each calendar month). You receive concrete recommendations for improvements. Free tier includes automated rule-based checks.

Can I cancel my MockArch Pro subscription anytime?

Yes. The Pro tier is billed month-to-month with no long term contracts. You will retain access to Pro features until the end of your billing cycle.

How is MockArch different from Miro or Excalidraw?

Those are general diagram tools. MockArch is built for system design interview prep: you get real-time cost estimates, load simulation, and on Pro, LLM feedback that suggests expert improvements. Interview scenarios and scoring are available on free tier for easy difficulty; medium and hard scenarios require Pro.

What are the core concepts of system design?

Core concepts include scalability (horizontal vs vertical), load balancing, caching strategies, database sharding, CAP theorem, and microservices architecture. MockArch helps you practice and visualize all these components interactively.

How to choose between SQL and NoSQL in a system design interview?

Choose SQL for structured data with complex relationships and ACID compliance requirements. Choose NoSQL for unstructured data, horizontal scalability, and rapid schema iteration. Use MockArch's simulator to compare the performance and cost tradeoffs of both.

How do load balancers work in system architecture?

Load balancers distribute incoming network traffic across multiple servers to ensure no single server bears too much demand, improving responsiveness and availability. In MockArch, you can drag and drop load balancers to see how they impact your system's bottleneck limits.

What is the best way to prepare for FAANG system design interviews?

The most effective preparation combines reading foundational texts (like Designing Data-Intensive Applications), practicing whiteboard problems, and using interactive simulators like MockArch. Pro includes deep LLM analysis to complement your practice; the free tier includes rule-based checks and simulation.

Can I estimate AWS cloud infrastructure costs?

Yes. MockArch acts as a dynamic infrastructure cost calculator. As you add databases, compute instances, and define traffic volumes, the simulator provides a real-time estimation of your monthly cloud spend.

PostgreSQL vs MongoDB | System Design Interview Tradeoffs

PostgreSQL

Relational Database

A powerful, open source object-relational database system with over 30 years of active development.

✅ Key Advantages

•Strict ACID compliance and data integrity
•Extremely powerful complex queries and JOINs
•Excellent support for JSON/JSONB (hybrid NoSQL behavior)
•Massive ecosystem of extensions (e.g., PostGIS for geospatial)

⚠️ Trade-offs

•Scaling writes horizontally is notoriously difficult
•Connection management overhead (requires PgBouncer at scale)
•Schema migrations can lock tables for large datasets
•MVCC implementation can lead to table bloat (requires vacuuming)

MongoDB

NoSQL Database

A source-available cross-platform document-oriented database program classified as a NoSQL database program.

✅ Key Advantages

•Flexible, schemaless JSON document structure
•Rich query language supporting aggregations and geospatial queries
•Horizontal scalability via native sharding
•Cloud-agnostic (can run on AWS, GCP, Azure, or on-premise)

⚠️ Trade-offs

•High memory consumption (loads working set into RAM)
•Lacks traditional ACID compliance across multiple documents (historically, though improved in recent versions)
•Sharding configuration can be operationally complex
•Data duplication is required for fast reads due to lack of JOINs

System Design Interview Metrics

Expected Latency

PostgreSQL~5-20ms (highly dependent on indexes and JOIN complexity)

MongoDB~1-5ms (reads from RAM), ~10-20ms (disk writes)

Cost Scaling

PostgreSQL

Scales via large vertical instances. Very cost-effective for complex relationships, but expensive to scale globally.

MongoDB

Usually provisioned instance based (e.g., MongoDB Atlas). Cost scales linearly with RAM and vCPU requirements.

Do not guess the costs in a system design interview. Prove it.

Simulate high-traffic workloads against both PostgreSQL and MongoDB using the MockArch canvas. Let AI analyze your architecture, scalability risks, and cost assumptions.

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