Top 5 Design Patterns Every Developer Should Learn

The patterns that separate junior developers from senior engineers

Three years ago, I was writing code that worked but was impossible to maintain. Functions stretched over 200 lines, classes did everything, and adding new features meant rewriting half the application.

Then I discovered design patterns.

Not the academic theory you find in textbooks, but the practical patterns that every senior developer uses instinctively. These aren't just interview talking points — they're the building blocks of maintainable, scalable software.

Today, I'm sharing the 5 patterns that transformed how I write code and think about software architecture. Master these, and you'll never look at code the same way again.

Why Design Patterns Matter More Than Ever?

Before diving into the patterns, let's address the elephant in the room: "Aren't design patterns just over-engineering?"

Here's the reality from working at scale:

• Netflix uses the Observer pattern for its entire recommendation system

• Uber built their surge pricing with the Strategy pattern

• Spotify playlist system relies heavily on Factory patterns

• Amazon's shopping cart uses the Command pattern for undo operations

These aren't academic exercises. They're proven solutions to recurring problems that every developer faces.

Pattern #1: Observer Pattern - The Event Notification System

What It Solves

Ever needed to update multiple parts of your application when something changes? Without the Observer pattern, you end up with tightly coupled code that's impossible to maintain.

How It Works

The Observer pattern defines a one-to-many dependency between objects. When one object changes state, all dependents are automatically notified.

Real-World Example

Think of YouTube subscriptions. When a creator uploads a video:

• Subscribers get notifications

• Recommendation algorithm updates

• The analytics system logs the event

• CDN starts caching the new content

All these systems "observe" the upload event without knowing about each other.

Code Impact