What is Monolithic Architecture?
A monolithic application is built as one single unit where:
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UI
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Business logic
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Database access
are all tightly coupled and deployed together. 
📌 Example:
One WAR/JAR contains user management, payments, orders, notifications — everything.
Characteristics:
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Single codebase
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Single deployment
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Shared database
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Tight coupling
Problems:
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Difficult to scale specific features
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One bug can crash the entire app
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Slow deployments
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Hard to adopt new technologies
🔹 What is Microservices Architecture?
Microservices break an application into small, independent services, each responsible for one business capability.
📌 Example:
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User Service
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Order Service
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Payment Service
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Notification Service
Each service:
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Has its own database
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Can be deployed independently
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Communicates via REST/Kafka
🔹 Key Differences
| Feature | Monolithic | Microservices |
|---|---|---|
| Deployment | Single unit | Independent services |
| Scalability | Hard | Easy & selective |
| Failure Impact | Entire app affected | Isolated failures |
| Technology Stack | One stack | Polyglot (different tech allowed) |
| Dev Speed | Slower | Faster, parallel teams |
| Maintenance | Difficult | Easier |
🔹 Real-World Example
E-commerce App
Monolith:
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Checkout bug → entire app goes down
Microservices:
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Payment service failure → catalog & cart still work
🔹 When to Choose Monolith?
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Small team
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Simple application
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MVP or early-stage startup
🔹 When to Choose Microservices?
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Large system
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High traffic
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Independent scaling needed
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Multiple teams