What methods can be used to split a monolithic application into more modules or services?

The separation of a monolithic application into smaller modules or services can be achieved through the following methods:

1. Modularization — isolating logically independent parts of the application into separate modules or libraries within a single codebase.

2. Service-Oriented Architecture (SOA) — dividing the application into services that interact through standardized interfaces (e.g., SOAP).

3. Microservices Architecture — a finer and more independent division into services, each responsible for a specific business function and deployed separately.

4. Use of APIs and contracts — isolating functionality through well-defined APIs, allowing parts of the application to be separated and developed independently.

5. Refactoring and layering — dividing the application into layers (e.g., presentation, business logic, data access) with subsequent separation of each layer into a separate module or service.

6. Use of containerization — packaging services into containers (Docker), which facilitates deployment and scaling of individual parts.

Example: separating the authentication module from the monolith into a separate microservice with REST API, which will be used by other parts of the system.