Definition of Microservices

Microservices is an architectural style that structures an application as a collection of small, autonomous services, each modeled around a specific business domain. These services communicate over a network (often HTTP/REST or messaging queues) to fulfill business requirements.

Advantages of Microservices Over Monolithic Architectures

1. Scalability:
   • Microservices: Individual services can be scaled independently based on their specific needs. For example, if the payment processing service experiences high load, it can be scaled out without affecting other services like user management.
   • Monolithic: The entire application must be scaled as a single unit, which can be inefficient and costly.
2. Fault Isolation:
   • Microservices: Failures in one service do not necessarily impact others. If the payment service fails, the user management service can continue to operate.
   • Monolithic: A failure in any part of the application can potentially bring down the entire system.
3. Technology Diversity:
   • Microservices: Each service can use the technology stack most suited to its requirements, allowing for greater flexibility and optimization. For example, a recommendation service might use machine learning libraries while an inventory service uses a traditional relational database.
   • Monolithic: The entire application is typically constrained to a single technology stack, which may not be optimal for all components.
4. Development Speed and Autonomy:
   • Microservices: Teams can work on different services independently, allowing for parallel development and faster release cycles. Each team can deploy their service without coordinating with others, as long as the API contracts are maintained.
   • Monolithic: Development is often tightly coupled, requiring significant coordination among teams. This can slow down the development process, especially for larger applications.
5. Deployment Flexibility:
   • Microservices: Individual services can be deployed independently, enabling continuous delivery and integration practices. This reduces downtime and allows for frequent updates.
   • Monolithic: Deploying changes typically requires rebuilding and deploying the entire application, which can lead to longer deployment times and increased risk of downtime.
6. Maintainability:
   • Microservices: Smaller, more focused codebases are generally easier to understand, maintain, and test. Refactoring a small service is less risky and more manageable than refactoring a large monolith.
   • Monolithic: A large, tightly coupled codebase can become difficult to maintain and understand over time, leading to technical debt and reduced agility.
7. Resilience and Fault Tolerance:
   • Microservices: Designed with resilience in mind, microservices can incorporate patterns such as circuit breakers, retries, and fallbacks to handle failures gracefully.
   • Monolithic: Handling failures in a monolithic application can be complex, as any part of the application failing could potentially bring down the entire system.
8. Focus on Business Capabilities:
   • Microservices: Each service is aligned with a specific business capability, making it easier to develop and evolve services in line with business requirements.
   • Monolithic: Business logic is often intermixed, making it harder to evolve specific business capabilities independently.
9. Improved Data Management:
   • Microservices: Each service can manage its own database, leading to improved data encapsulation and ownership. This also allows for different data storage technologies to be used where appropriate (polyglot persistence).
   • Monolithic: A single database is typically shared across the entire application, which can lead to tight coupling and difficulties in managing data schema changes.

Example Scenario: Payment Processing in Asset Leasing

Microservices Approach:

• Mandate Management Service: Handles mandate registration, updates, and lifecycle.
• Payment Processing Service: Processes payments based on schedules using either file-based or GoCardLess.
• Receipt Management Service: Manages receipts for successful payments.
• Reversal Service: Handles reversal of payments in case of failures.

Each service can be developed, deployed, and scaled independently, providing a highly flexible and resilient system.

Monolithic Approach: