What is Microservices

Bigger project is broken into independent modules/processes(called microservice) running on independent VM or Docker container. Size of microservices can vary from 100 LOC to 10k.
Microservices are stateless because new MS boots in to serve existing request, it should not care about states.

Advatanges of Microservices

1. Independent deployble modules: All teams can work independently of each other. Teams can make their own technology decisions.
2. Adopting New Technology: Developers can employ a completely new technology stack (without affecting the others).
3. Easy replacement: Complete microservice can be re-engineered or replaced easily, without affecting other microservices
4. Resilience: If 1 microservice of a system fails, failure will not cascade to rest of the system. Rest of system can carry on working.
5. Scaling: Each microservice can be scaled independently.

Disadvatanges of Microservices

1. Increased Operation effort: MS system have many more units wrt deployment monolith hence requires larger operations efforts
2. Increased Latency: MS communicate over network, hence will take more time wrt file based communication.
3. Testing all microservice together: if 1 microservice is broken, it will break whole system.

Deployment Monolith

All components are integrated into a single codebase.

Advantages of Monolith

1. Simplicity in Development: With everything in one place, development is often faster and simpler, making it easier for new team members to onboard
2. Ease of Deployment: Deploying a monolithic application involves managing fewer moving parts
3. Simplified Testing: all components are part of a single unit, allowing for efficient end-to-end testing without complex inter-service communication
4. Low Latency: Since all components run within the same process, IPC takes less time.

Disadvantages of Monolith

1. Scalability Challenges: If 1 module need more resources, entire application must be scaled up, since other modules might not function with new resource, this leads to unneccessary time wastage.
2. Slower Development Speed: Dev1 working on part1, dev2 on part2. Integration testing might need more time. dev1 might use lib1 and dev2 lib2
3. Technology Constraints: challenging to adopt new technologies or frameworks without significant rework
4. High Dependency Risks: An issue in one component can affect the entire application’s functionality.

Situations where monolithic is suitable

1. Startups and Small Teams: Small teams (2 to 5 members), a monolithic architecture allows for faster development and deployment
2. Proof of Concept Development: Creating MVP(Minimum Viable Product)
3. Simple Non-Scalable Application: If application has simple functionality and does not have complexity or scalability demands
4. Min Latency required: Spacecraft system. A delay of microseconds b/w component communication is not acceptable
5. Less Operational Complexity: For systems which need less Operational complexity, monolith is preferred.

Microservice vs Deployment Monolith