System Design Building Blocks

Kay Ashaolu - Instructor

Aishwarya Sriram - TA

Building Blocks: Introduction

• Storage + Tasks = Building Block
• Reusable, purposeful units
• Essential for robust architecture

Motivation & Recap

• Everything reduces to bits: zeros and ones
• Bits represent Storage (data) and Tasks (instructions)

Storage Units

• Represent structured data
• Examples: lists, arrays, dictionaries, trees, graphs
• Organize data and define relationships

Task Units

• Represent instructions
• Executed by CPUs/GPUs
• Examples: functions, methods, services

Building Blocks Defined

• Combination of Storage and Task units
• Purposeful, reusable components
• Examples: User services, Payment gateways, Search engines

Why Building Blocks?

• Mirror real-world logic
• Self-contained data and behavior
• Form intuitive, stable, complex systems

Example: Simple Web Server

• Waits for requests
• Returns files (HTML, images)

Server Building Block

• Storage: URL paths as keys
• Task: Instructions generating responses
• Maps URL to task handlers

Server Internals: Routing Table

• Dictionary storage unit
• URL path → Task handler

routing_table = {
    "/": home_page,
    "/post/1": post_one_page,
}

Tasks as Request Handlers

• URL path → Specific Task unit
• Executes instructions
• Returns response

File System Building Block

• Tree-based storage
• Hierarchical file paths
• Retrieves raw data

File System Structure

• Organized hierarchically

public_html/
├── post/
│   ├── 1.html
│   └── 2.html

Interaction: Server & File System

• Server receives URL path
• Task requests file from File System
• File System returns data
• Server sends data to user

Architecture Diagram

User → Server → Task Unit → File System → User

Summary: Static Web Server

• Server handles requests
• File System provides file data
• Building blocks create holistic system

Building Blocks & Intuition

• Data structures: Storage Units
• Algorithms: Task Units
• Modules/Components: Building Blocks

Building Blocks as Architecture

• Combine blocks into architectures
• Understand strengths, weaknesses
• Enables debugging, scaling, evolving

Gaining Senior-Level Intuition

• Recognize common patterns
• Understand why decisions are made
• Anticipate architecture behavior

Practical System Design Approach

• Define clear requirements
• Match building blocks to needs
• Learn through case studies

The Seven Building Blocks

Worker

Service

Key-Value Store

File Store

Queue

Relational Database

Vector Database

External Entities

Wrap-Up

• Building blocks are core principles
• Develop intuition over memorization
• Technology agnostic approach