Introduction

System Design is the process of defining the architecture, components, and interactions of a system to satisfy specified requirements. At its core:

System = Components + Common Goal

All components within a system work together to achieve a unified objective, whether it's handling user requests, processing data, or delivering services reliably at scale.

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Understanding System Design Through a Real-World Analogy

Consider a bank called AlienBank with a simple cash counter.

Basic Banking Flow

Components in the System

• Customer
• Cash Counter
• Cashier
• Receipt System
• Database

Customer Flow Cycle

1. Customer comes to the counter
2. Customer requests withdrawal/deposit
3. Cashier processes the request
4. Receipt is generated
5. Transaction completed

Initially, the system works fine when the number of customers is small.

But as usage increases, different problems start appearing.

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Problems and Solutions — Mapping to System Design Concepts

Issue 1: Process is Slow

Problem: Each customer takes ~10 minutes due to:

• Understanding requirements
• Counting cash manually
• Preparing the receipt

Solution: Optimize the process to reduce time to ~5 minutes per customer.

• Train the cashier to count faster
• Train the cashier to type faster

System Design Mapping:

Issue 2: Customer Count is Increasing

Problem: A single counter cannot handle growing demand.

Solution: Upgrade the counter's capacity.

• Increase desk size
• Introduce a cash counting machine
• Pre-fill forms before reaching the counter
• Reduced time to ~3 minutes per customer

System Design Mapping:

Issue 3: Customer Waiting Time is High

Problem: Even with optimizations, a single counter creates a bottleneck during peak hours.

Solution: Add more cashiers and more counters.

System Design Mapping:

Issue 4: Data Discrepancy

Problem: Counter 1 and Counter 2 each maintain their own data. If they are not in sync, inconsistencies arise (e.g., incorrect account balances).

Solution: Introduce a centralized database that all counters read from and write to, ensuring a single source of truth.

System Design Mapping:

Issue 5: Underutilized Counters

Problem: Some counters are overloaded while others sit idle — leading to uneven resource usage.

Solution: Introduce a middleman who checks the load on each counter and directs customers accordingly.

System Design Mapping:

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Complete Analogy-to-System Mapping

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Key Takeaways of System Design Concepts

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Summary

• System Design focuses on building scalable and efficient systems capable of handling increasing traffic, complexity, and performance demands as the user base grows.

• Scalability is achieved through two primary approaches: Vertical Scaling (increasing server capacity) and Horizontal Scaling (adding more servers to distribute workload).

• In distributed systems, maintaining data consistency and synchronization across multiple servers is critical to avoid data discrepancies and ensure reliable operations.

• Load Balancers play a vital role in distributing requests efficiently, preventing server overload, improving performance, and optimizing resource utilization.

• A well-designed system should be scalable, reliable, efficient, maintainable, and fault-tolerant to support long-term growth and operational stability.

Written By: Muskan Garg