Overview of Distributed Systems

Monolithic Systems

• Large, single codebase bundling all functionality together
• Simple deployment but difficult to maintain and scale
• All components interconnected within one system
• Changes to one part can impact the entire application
• Lack of modularity makes maintenance increasingly difficult as application grows

Distributed Systems

• Split large systems into smaller, independent modules
• Each module developed and maintained individually
• Modular design encourages ownership and reduces impact of changes
• Better scalability and simplified maintenance
• Modules communicate with each other to perform tasks

Real-World Example: Customer Order Processing

When a customer places an order:

• Order Service receives the request
• Warehouse module handles dispatch
• Email Service sends order confirmation
• Each service operates independently while collaborating

Communication Methods

Direct Communication

• Services connect directly using IP addresses
• Simple but creates tight coupling between services
• Fragile: breaks if IP changes or service goes down
• Example: Order Service → Warehouse (10.1.1.1), Email Service (10.1.1.2)

Messaging System Communication

• Services communicate through a messaging platform
• Decouples services for independent operation
• Messaging system handles routing and queuing
• Messages queued if service temporarily unavailable
• Enhanced resilience and scalability
• Services can be added/removed without breaking communication