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.

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.

System Design Simulator

Simulate system design decisions before your architecture interview

Build a proposed architecture, apply realistic traffic assumptions, and see how latency, capacity, and cost change as your design evolves.

Open the Simulator Explore Scenarios

Drag and drop APIs, services, queues, databases, caches, CDNs, and load balancers.

Estimate infrastructure cost and latency impact while you refine the design.

Practice explaining scalability, availability, and failure-mode tradeoffs with evidence.

Traffic simulation

Set workload assumptions and evaluate whether your architecture can absorb realistic request volume.

Cost estimation

Estimate monthly infrastructure cost so your system design interview answer includes practical business tradeoffs.

Scalability review

Spot bottlenecks in compute, storage, caching, queues, and load balancing before they weaken your interview response.

System Design Interview FAQ

Common system design interview questions

How do I practice system design interviews online?

Start with a realistic system design interview question, build the architecture, explain tradeoffs, and review feedback. MockArch combines a diagram canvas, traffic simulation, cost estimates, and AI feedback so practice feels closer to a real senior engineering interview.

What makes MockArch a system design interview simulator?

MockArch lets you model APIs, databases, caches, queues, load balancers, traffic volume, latency, and cost. Instead of only drawing boxes, you can test whether the architecture handles scale and then improve it based on scoring and feedback.

Do I need a credit card to start?

No. Sign up and use the free tier, including up to 3 saved designs, easy scenarios, rule-based analysis, cost and traffic simulation, and export as image without a card. LLM deep analysis requires Pro.

Can I cancel anytime?

Yes. Pro is month-to-month. Cancel anytime and you keep access until the end of your billing period. No long-term contract.

What's included in the free tier?

Up to 3 saved designs, full component palette, cost and traffic simulation, rule-based standard analysis, easy interview scenarios with scoring, and export as image. Medium and hard scenarios, unlimited saved designs, and LLM deep analysis up to 20 per UTC calendar month on Pro require Pro.

How is MockArch different from Miro or Excalidraw?

Those are diagram tools. MockArch is built for system design interview prep: you get real-time cost estimates, load simulation, and on Pro, AI feedback that scores your design and suggests improvements like a staff engineer in the room.

Is my data secure?

Designs are stored securely. We use secure payment processing. We do not sell your data. You can export and delete your work anytime.

How does AI feedback work?

Pro includes Up to 20 AI deep analyses per calendar month (UTC). Resets at 00:00 UTC on the first day of each calendar month. You get feedback on bottlenecks, scaling, security, and concrete improvements. Free tier includes automated rule-based checks only.

Still have questions? Explore system design interview practice or start free and see for yourself.