Monolith vs Microservices in .NET Core
1. Monolithic Architecture
- Definition: A single, unified codebase where all modules (UI, business logic, data access) are part of one large application.
- Deployment: Deployed as a single unit (e.g., oneÂ
.exe orÂ.dll). - Scaling: Scales by cloning the entire application (vertical/horizontal scaling).
- Communication: Internal method calls (no network).
- Tech Stack: Typically limited to a single framework/runtime.
- Example in .NET Core:
- An ASP.NET Core MVC app with controllers, services, and EF Core all in the same project.
- Single database, one codebase, deployed to IIS/Kestrel.
2. Microservices Architecture
- Definition: A collection of small, independent services, each responsible for a specific business function.
- Deployment: Each service runs independently (often in Docker containers).
- Scaling: Scale individual services based on demand.
- Communication: Via APIs (REST, gRPC, message queues).
- Tech Stack: Each service can use different frameworks/languages (polyglot).
- Example in .NET Core:
- Separate Order Service, Payment Service, User Service.
- Each service is its own ASP.NET Core Web API with its own database (Database-per-service).
- Uses API Gateway (Ocelot/YARP) for routing.
- Runs in Docker & Kubernetes.
🔹 Key Differences
| Feature | Monolith (.NET Core) | Microservices (.NET Core) |
|---|---|---|
| Codebase | Single, large project | Multiple smaller projects (per service) |
| Deployment | One unit | Independent deployments |
| Scalability | Entire app must scale | Scale only required service |
| Database | Usually one shared DB | Separate DB per service (Database-per-service pattern) |
| Technology | One stack (e.g., only .NET Core + SQL Server) | Polyglot (C#, Node.js, Python, SQL/NoSQL) |
| Communication | In-process calls | REST, gRPC, Message Bus (RabbitMQ, Kafka, Azure SB) |
| Fault Isolation | A bug can crash whole app | Failures isolated to one service |
| DevOps | Easier to deploy | Requires CI/CD pipelines, containers, orchestration |
| Best For | Small/medium apps with simple domain | Large, complex, high-scale, distributed systems |
🔹 When to Use What?
- ✅ Monolith:
- Small to medium apps.
- Simple business logic.
- Quick delivery required.
- Team size is small.
- ✅ Microservices:
- Large enterprise systems.
- Need for independent scaling & deployments.
- Multiple teams working on different modules.
- Cloud-native, containerized solutions.
💡 Interview Tip:
If asked in an interview, explain the trade-offs:
- Monolith is simpler but harder to scale/maintain as it grows.
- Microservices bring scalability and flexibility but add complexity in communication, monitoring, and DevOps.
