Introduction
This study explores the design and implementation of an information system, the MySchool System (an application for managing students, courses, and departments), through two distinct architectural approaches: the monolithic and the microservices. The monolithic approach unifies all functionality into a single project, while the microservices architecture decomposes the system into independent, smaller services. This example serves an educational purpose, aiming to clarify the practical differences between these two technological approaches in terms of code structure and overall system behavior.
The Monolithic Approach
The monolithic version of the MySchool System represents the classic development model. All subsystems – user management, student administration, course management, department oversight – reside within a single solution, share a common database, and run as one cohesive application.
Folder Structure Example:
MySchool/
│
├── Domain/
│ ├── Entities/
│ │ ├── User.cs
│ │ ├── Student.cs
│ │ ├── Lesson.cs
│ │ └── Department.cs
│ └── Interfaces/
│ ├── IStudentRepository.cs
│ ├── ILessonRepository.cs
│ └── IUserRepository.cs
│
├── Application/
│ ├── Services/
│ │ ├── AuthService.cs
│ │ ├── StudentService.cs
│ │ └── LessonService.cs
│ └── DTOs/
│ ├── LoginRequest.cs
│ └── StudentDto.cs
│
├── Infrastructure/
│ ├── Data/
│ │ └── MySchoolDbContext.cs
│ ├── Repositories/
│ │ ├── StudentRepository.cs
│ │ ├── LessonRepository.cs
│ │ └── UserRepository.cs
│ └── Migrations/
│
├── Presentation/
│ ├── Controllers/
│ │ ├── AuthController.cs
│ │ ├── StudentsController.cs
│ │ └── LessonsController.cs
│ └── Program.cs
│
└── appsettings.json
Architectural Diagram (Monolithic):
┌────────────────────────────┐
│ Presentation │
│ (Controllers, Swagger) │
└────────────┬───────────────┘
│
▼
┌────────────────────────────┐
│ Application │
│ (Services, DTOs, Business) │
└────────────┬───────────────┘
│
▼
┌────────────────────────────┐
│ Domain │
│ (Entities, Interfaces) │
└────────────┬───────────────┘
│
▼
┌────────────────────────────┐
│ Infrastructure │
│ (EF Core, DbContext, Repo) │
└────────────────────────────┘
Analysis:
The monolithic MySchool offers direct communication between layers, a fast build-deploy cycle, and low maintenance costs. It’s ideal for small teams and straightforward needs. However, as the system grows, its unified nature can create obstacles in terms of scaling and independent development of individual features.
The Microservices Architecture
In a microservices architecture, the same system is decomposed into distinct, autonomous services. Each service typically has its own database, its own domain model, and operates independently of the others.
Example Service Distribution:
- Auth Service: Manages users, roles, and JWT tokens.
- Student Service: Handles student registrations and profile information.
- Lesson Service: Manages courses, assignments, and instructors.
- API Gateway: Routes requests to the individual services.
Indicative Structure (Microservices):
MySchool.AuthService/
│ ├── Controllers/AuthController.cs
│ ├── Application/AuthService.cs
│ ├── Infrastructure/UserRepository.cs
│ ├── Domain/User.cs
│ └── Database: AuthDB
MySchool.StudentService/
│ ├── Controllers/StudentsController.cs
│ ├── Application/StudentService.cs
│ ├── Infrastructure/StudentRepository.cs
│ ├── Domain/Student.cs
│ └── Database: StudentDB
MySchool.LessonService/
│ ├── Controllers/LessonsController.cs
│ ├── Application/LessonService.cs
│ ├── Infrastructure/LessonRepository.cs
│ ├── Domain/Lesson.cs
│ └── Database: LessonDB
MySchool.APIGateway/
│ ├── Routes/
│ │ ├── /api/auth → AuthService
│ │ ├── /api/students → StudentService
│ │ └── /api/lessons → LessonService
│ └── Program.cs
Architectural Diagram (Microservices):
┌────────────────────────────┐
│ API Gateway │
│ (Routing & Auth Handling) │
└────────────┬───────────────┘
│
┌───────────────────────┼──────────────────────────┐
│ │ │
▼ ▼ ▼
┌────────────────┐ ┌────────────────┐ ┌────────────────┐
│ Auth Service │ │ Student Service│ │ Lesson Service │
│ JWT / Users │ │ Students Data │ │ Lessons Data │
│ AuthDB │ │ StudentDB │ │ LessonDB │
└────────────────┘ └────────────────┘ └────────────────┘
Analysis:
The microservices architecture transforms the MySchool System into a collection of small, agile applications. Each can be developed, deployed, and scaled independently. The infrastructure becomes more complex, requiring mechanisms for inter-service communication, monitoring, service discovery, and integration via an API Gateway. Nevertheless, the flexibility it provides is immense for large-scale environments.
Conclusion: Architecture as a Tool
System architecture is a tool, not an end in itself. The MySchool System clearly demonstrates that the choice between monolithic and microservices approaches depends entirely on the organization’s size, strategy, and business needs.
The monolithic version is a natural starting point, offering speed, simplicity, and unified management. It’s ideal for small teams, MVP products, or educational systems with low scaling requirements. Conversely, when the system expands to multiple functionalities, when multiple teams need to work independently, or when performance and availability requirements become critical, then the transition to microservices is not only natural but necessary.
Ultimately, an architect’s maturity is not shown by the complexity of the architecture they choose, but by their ability to maintain the right balance between simplicity and scalability. A smart system evolves with its needs – starting simply, but ready to transform when scale demands it.
The Critical Transition Point: When to Break Apart the Monolith
The transition to microservices isn’t driven by trends but by fundamental shifts in data, users, workflows, and rates of change, where the monolithic approach ceases to be sustainable. Three main categories of signals indicate this tipping point:
1. Data Volume and Flow
When the data flow within the system becomes so large that different functionalities have varying resource demands, the monolith begins to struggle.
Example: A MySchool System initially handles 100 students, 10 courses, and 3 administrators perfectly on a shared database. If it evolves into a nationwide educational platform with 300,000 students, 50,000 courses, thousands of requests per hour for registrations, exams, and results, and concurrent connections from parents, teachers, and schools, the monolith will slow down significantly. The database will face heavy queries, controllers will lag, indexes will saturate, and transactions will block.
Signal: When each domain has different performance and I/O requirements (e.g., Auth is read-heavy, Exams are write-heavy, Students are analytics-heavy), you’ve surpassed the point of balance. It’s time to decompose domains into independent services with their own databases.
2. Organizational Scale and Development Pace
As development teams grow, collaborating on a monolithic codebase becomes increasingly challenging.
Example: Initially, 3 developers work on the same repository with no issues. Later, 15 developers across 3 teams (Auth, Students, Lessons) experience conflicts with every change to Program.cs or DbContext. Every deployment involves the entire system, and a bug in a small module (e.g., Auth) can halt production for everyone.
Signal: When teams cannot develop, deploy, and test independently without waiting for other teams, it’s time for microservices.
3. Independent Business Domains
If the system starts to encompass multiple distinct areas of responsibility that could function autonomously, natural “service boundaries” emerge.
Example: The MySchool system expands to include:
- Auth & Identity (login, roles, tokens)
- Academics (courses, exams, grades)
- Payments (tuition, subscriptions)
- Analytics (performance statistics)
- Notifications (emails, SMS, alerts)
If each module has its own development cycle, different data, and separate business logic, the system implicitly calls for separation.
Signal: When areas of responsibility are clearly independent and communicate via well-defined boundaries, microservices become the next logical step.
Key Indicators for Transition
The following criteria indicate a need for microservices if two or more apply:
- Database Size: > 10 GB of active transactional data – indicates difficulty in scaling the database and a need for distribution.
- Intensive Operations per Second: > 1,000 API calls/sec – requires independent scaling.
- Developers: > 8-10 in one team – difficult collaboration on a common repository.
- Different Change Cycles: Yes (e.g., Auth develops quickly, Lessons rarely – a mismatch).
- Disruptions Due to Unified Deployments: Yes (when downtime of one module affects the entire system).
- Different Technological Needs: Yes (e.g., Analytics needs Python, Auth needs .NET).
If you observe two or more of these conditions, you’ve likely passed the tipping point. The monolith is no longer efficient – you need decomposition into services.
The Golden Rule of the Architect
“Don’t start with microservices. Start monolithically – but build in such a way that you can break it apart when the time comes.”
This means:
- Maintain clear boundaries between modules (e.g., Application layer does not depend on Infrastructure).
- Create clean interfaces between domains.
- Establish an abstraction layer for communication (e.g., StudentService → IStudentRepository).
This modular design ensures that when the time comes to “extract” the StudentModule into its own service, you can do so without collapsing the entire system.
Example of Evolution
- Phase 1 – Monolithic: Controllers → Services → DbContext
- Phase 2 – Modular Monolith: Each domain in its own folder, with its own interfaces.
- Phase 3 – Microservices: Each module as an independent service with its own DB and API endpoints.
Remember:
The critical transition point is not a mere technical number, but a combination of three factors:
- Data and its flow become heterogeneous and heavy.
- Teams and their development pace cannot operate on a common codebase.
- Domains acquire independent business substance.
When these three factors align, your architecture is essentially “asking” for microservices – not because it’s a trend, but because it’s how it can survive and thrive.