System Design in 30 Days: A Practical Learning Roadmap

System design can feel overwhelming when every architecture diagram introduces ten unfamiliar components at once. Load balancers, caches, queues, databases, gateways, retries, and consistency models all appear connected—but it is rarely clear where a beginner should start.

System Design in 30 Days solves that problem by teaching one practical concept at a time. Each lesson explains what a building block does, when it is useful, what trade-off it introduces, and how it connects to the larger system.

By the end of the series, you should be able to look at a system-design problem, break it into smaller decisions, state reasonable assumptions, and explain why you selected particular components. The goal is not to memorize a perfect architecture. It is to develop a repeatable way of thinking.

This page is the central roadmap for the complete series. Bookmark it and return whenever you want to find the next lesson, blog, notes, or practice question.

Who is this series for?

This series is designed for:

• software-engineering students learning system design for the first time;

• frontend, backend, mobile, or full-stack developers who want a clearer architecture foundation;

• engineers preparing for system-design interviews;

• developers who know individual technologies but struggle to connect them into a complete system; and

• anyone who wants a structured revision path without beginning with an enormous architecture diagram.

You do not need prior distributed-systems expertise. Basic familiarity with applications, APIs, databases, and client-server communication will help, but every lesson begins with a simple mental model.

What will you learn in 30 days?

The journey progresses through five connected stages.

Stage 1: Traffic, capacity, and scale

You will learn how requests enter a system, how to estimate demand, and how systems grow beyond a single server.

1. Day 1 — Load Balancing

2. Day 2 — Capacity Estimation

3. Day 3 — Vertical vs Horizontal Scaling

4. Day 4 — Caching

5. Day 5 — Content Delivery Networks

Stage 2: Data storage and consistency

You will compare database models, improve query performance, distribute data, and reason about consistency during failures.

1. Day 6 — SQL vs NoSQL

2. Day 7 — Database Indexing

3. Day 8 — Database Replication

4. Day 9 — Database Sharding

5. Day 10 — CAP Theorem

6. Day 11 — Strong vs Eventual Consistency

7. Day 12 — Consistent Hashing

Stage 3: Communication, APIs, and asynchronous work

You will learn how services exchange information, buffer work, publish events, protect endpoints, and support different communication patterns.

1. Day 13 — Message Queues

2. Day 14 — Publish-Subscribe

3. Day 15 — Event-Driven Architecture

4. Day 16 — Rate Limiting

5. Day 17 — API Gateway

6. Day 18 — Forward vs Reverse Proxy

7. Day 19 — Polling vs WebSockets

Stage 4: Reliability, coordination, and architecture

You will explore the patterns that make retries safer, limit cascading failures, coordinate distributed work, and organise services as systems evolve.

1. Day 20 — Idempotency

2. Day 21 — Retries and Exponential Backoff

3. Day 22 — Circuit Breakers

4. Day 23 — Distributed Locks

5. Day 24 — Service Discovery

6. Day 25 — Monolith vs Microservices

7. Day 26 — Saga Pattern

Stage 5: Apply the building blocks

The final four days combine earlier concepts into complete case studies. The focus is not a single “correct” diagram; it is learning how requirements and trade-offs shape the design.

1. Day 27 — Design a URL Shortener

2. Day 28 — Design WhatsApp Message Delivery

3. Day 29 — Design Netflix Streaming

4. Day 30 — Design the Instagram Feed

How does each daily lesson work?

Every day follows the same learning loop:

The videos provide the first explanation. The daily blogs go deeper and contain the assumptions, calculations, examples, comparisons, and common mistakes that cannot fit inside a short Reel.

Where can you find the blogs and notes?

Use this page as the series homepage:

korshub.com/blog/system-design-in-30-days

Each lesson above links to its day-specific blog. Published articles will also include navigation back to this roadmap and forward to the next available lesson.

Downloadable notes will appear inside the corresponding daily blog, so the video, explanation, exercise, and revision material stay together.

A simple method for approaching system design

Across the series, use this four-question framework:

1. What must the system do? Identify the essential user actions and constraints.

2. How much work must it handle? State assumptions and estimate traffic, storage, and bandwidth when relevant.

3. Which building blocks fit those needs? Choose components because they solve a stated problem—not because they appear in popular diagrams.

4. What trade-off did each choice introduce? Consider complexity, cost, consistency, availability, latency, and operational effort.

This framework keeps the design grounded in requirements. A small product and a global platform may use different architectures even when they provide similar user features.

Try this today

Before Day 1, choose one application you use regularly. It could be a messaging app, shopping platform, video service, food-delivery app, or workplace tool.

Write down:

• the three most important user actions;

• one part of the experience that must feel fast;

• one failure users would find unacceptable; and

• one question you currently cannot answer about its architecture.

Keep this application as your personal case study. Revisit it after each lesson and ask where the day’s concept might fit.

Copy this 30-day learning log

Use the following template after every lesson:

Day and topic:
The problem this concept solves:
My one-sentence mental model:
Important assumptions or units:
One benefit:
One trade-off:
Where I might use it:
One question I still have:

For example, after Day 1 you might write: “A load balancer gives clients one entry point and distributes requests across healthy servers. It can improve availability and spread traffic, but it also requires health checks and careful configuration.”

Common mistakes to avoid

Memorising diagrams without understanding requirements

A component is useful only when it addresses a real constraint. Begin with the problem, scale, and trade-offs before selecting technology.

Treating every system as internet-scale

Most products do not need the architecture of a global streaming platform on their first day. Design for stated requirements and explain how the system could evolve.

Ignoring assumptions

Capacity calculations are estimates, not promises. Write down assumptions, keep units consistent, and distinguish average demand from peak demand.

Searching for one perfect answer

System design involves choices. Two different designs can both be reasonable when their assumptions, priorities, and trade-offs are explained clearly.

Learning components in isolation

Do not stop at “what is a cache?” Also ask what data belongs there, how entries expire, what happens when it fails, and how it interacts with the database.

Quick knowledge check

1. What is the main goal of this series?
   To develop a structured way to reason about system-design problems, not merely memorise architecture diagrams.

2. Where should you find each day’s detailed explanation and notes?
   In the corresponding daily blog linked from this central roadmap.

3. What should come before choosing components?
   Requirements, constraints, assumptions, and a basic estimate of the work the system must handle.

4. Does every system need the same architecture?
   No. The appropriate design depends on scale, reliability needs, consistency requirements, team constraints, and accepted trade-offs.

Continue learning with Korshub

The daily lessons are designed to give you a clear learning path. When you want longer explanations and guided examples, explore these Korshub courses:

• Rocking System Design for the general foundations;

• Mastering the System Design Interview for interview-oriented practice;

• Software Architecture: Design of Modern Large-Scale Systems for architecture concepts;

• Software Architecture & System Design: Practical Case Studies for applied designs; and

• The Complete Microservices & Event-Driven Architecture for messaging, events, and service-based systems.

Course availability and details can change, so use the linked course pages as the current source of information.

Frequently asked questions

Is Day 0 part of the 30 lessons?

No. Day 0 is the introduction and central roadmap. The technical learning journey begins with Day 1 and ends with Day 30.

Can beginners follow this series?

Yes. The lessons begin with foundational building blocks and gradually combine them into larger systems. Basic knowledge of applications, APIs, and databases is helpful but advanced distributed-systems knowledge is not required.

Should I follow the days in order?

Following the sequence is recommended because later lessons reuse earlier mental models. If you already understand a topic, use its blog and exercise as a revision checkpoint.

How much time should I spend each day?

Watch the short lesson, read the supporting blog, complete the exercise, and record the concept in your learning log. The exact time will depend on your existing knowledge and how deeply you explore the example.

Where will new lessons be added?

New daily blogs will be linked from this roadmap. Bookmark this page so you always have one starting point for the complete series.

Start Day 1

Your first lesson is Load Balancing: how one entry point can distribute requests across healthy servers.

Next: Day 1 — Load Balancing
Roadmap: System Design in 30 Days
Previous: Series introduction