From Monolithic .NET to .NET Core Microservices: Migration Guide

Finding a proper definition of .NET migration is like comparing a department store and a street market. The first one, monolithic, has everything a buyer needs under one roof, but if the front door jams, the entire system halts. While in the street market, like microservices, each vendor runs independently. If the fruit stall has issues, the electronics stall still works fine. The same thing, microservices are more flexible and easier to scale under real-world conditions.

Although going to a microservices-based architecture increases the software scalability, flexibility, and maintainability, certain difficulties arise with the shift. In this thorough, step-by-step tutorial, we’ll examine how to effectively convert a .NET monolithic application to .NET Core or 7+ microservices. Ready to begin? Let’s get started.

Understanding Monolithic vs. Microservices Architecture: What Is a .NET Migration?

The process of .NET migrations transforms a traditional, tightly coupled .NET monolithic application into a decoupled, modular, microservices-based system in .NET 8 or the latest .NET 9. It’s complex and comprehensive, so developers apply various techniques, such as the Strangler Fig Pattern, which allows gradual refactoring. According to it, the monolithic services are replaced one by one, so over time, a monolith becomes a set of microservices.

Still, migration is a complex process. In their pursuit to make it easier to oversee it, developers apply special metrics, in particular, a .NET migration rate. This rate measures how much monolithic functionality is successfully converted to microservices. Moreover, there are pitfalls waiting in the process. Thus, a solid understanding of your application’s architecture and operational environment is essential to a successful .NET migration.

When to Migrate? A Brief Checklist

The new .NET Core/.Net 7+ architecture is generally more cost-effective in the long run, especially for modern, scalable, and cloud-based applications. However, the cost of migration might be significant, so you might start migration only when it’s a strategic move. Look at the .NET migration example in the form of a table. It shows some common signals to prioritize transition:

These are clear signs it’s time to consider a .NET migration and start moving toward a more flexible, modern, microservices-based setup.

.NET Migration Guide That Makes Complex Changes Feel Simple

Now that the foundation has been established, let’s go over the actual procedures for successful .NET migrations, from evaluation to deployment and optimization.

Rule number one is that the business capabilities, not horizontal layers, are the ones that should guide the architecture of microservices. So, let’s move from general to specific.

Step 1: Assess Your Monolithic Application

The first step is preparatory. Before moving forward, evaluate your application to avoid unforeseen issues and wasted effort during migration as follows:

• Understanding the Current Architecture: Document relationships, interactions, and components to gain an understanding of the current architecture.
• Recognizing Bottlenecks: Look for problems with maintainability, scalability, or performance.
• Assessing Business Domains: Determine which domains are suitable for isolation as services.
• Apply Domain-Driven Design (DDD): It requires a good retrospective understanding of the domain for which the application is written:

1. Identify a ubiquitous language. Make sure the code uses business terms that are understandable to non-technical people. The code should serve the business processes.
2. Sort out monolithic application components: which are pertinent, and which are not. Then apply the common vocabulary to those modules.
3. Define bounded contexts. The bounded contexts that you identify are candidates to be refactored into smaller microservices.

That’s it. Now, you’re ready to proceed to the next step.

Step 2: Define Boundaries of Microservices

After the principles of DDD are implemented in order to proceed with .NET migration, we need to establish the service limits. Thanks to the strict boundaries of microservices, we avoid overlapping responsibilities and ensure each service evolves independently. Clear boundaries help prevent tight coupling, improve maintainability, and allow teams to scale development more efficiently, so it’s worth the effort. This is how we achieve effectiveness:

• Each service should have one obligation, according to the single responsibility principle,
• Each service should have a distinct data ownership,
• Start with loosely linked modules,
• Focus on dependencies from data or other modules: their type and scale, and the potential effects on other modules of a modification to the selected module. Because if you transfer features first and then data, you may be momentarily reading from and writing to several databases. As a result, you’ll need to synchronize and check data integrity,
• Extract modules with different resource requirements compared to the rest of the monolith. For instance, you can turn a module with an in-memory database into a service so that it can be used on servers with more memory. You can greatly simplify the scalability of your application by converting modules with specific resource requirements into services.

Business goals, thorough test coverage, the application’s security posture, and organizational buy-in are the elements that may influence your service migration decisions.

Step 3: Choose the Right Technology Stack in .NET

Choosing the right stack for .NET migration is vital for a stable, scalable system, so let’s explore the possible variants:

• .NET 8+: For cross-platform compatibility and contemporary functionality. .NET 10 is the latest long-term-support version, ideal for new projects.
• ASP.NET Core: Perfect for creating web APIs with great performance,
• Entity Framework Core: Flexible Multiple database access,
• Docker: Containerize services for easier deployment and consistency.

With this tech foundation in place, the next step is to design your system for resilience and scalability.

Step 4: Design for Scalability and Resilience

This step is about architectural readiness. After deciding on a stack for .NET migration, you need to design services to handle scale, fail gracefully, and operate reliably in distributed environments. Here are some practices:

• Stateless Services: Use horizontal scaling,
• Circuit Breakers: Avoid cascading failures,
• Load Balancing: Manage traffic evenly across instances,
• Introduce an IPC (Inter-Process Communication) Adapters: To let the freshly detached microservice and the monolith communicate via well-defined APIs without being closely coupled.

Let’s expand the last item in detail. In the context of .NET migration, IPC is used to let the old monolithic components and the new microservices coexist. Instead of rewriting everything at once, you move gradually. You extract parts of the system and let them talk via APIs or adapters.

Let’s break down how to implement an API gateway in the next section.

Step 5: Implement an API Gateway

APIs are usually used to share data when the core capabilities or modules are divided into microservices. The above-mentioned diagram illustrates how the referenced service provides data as an API required by the caller service. To connect the services, use the following approaches:

• YARP (Yet Another Reverse Proxy): Build a high-performance gateway in .NET. It helps manage load balancing, routing rules, authentication, and other intersecting issues. YARP is adaptable to dynamic routing and contemporary deployment patterns like Kubernetes-based service discovery because it can be configured via code or JSON.
• Routing and Middleware: Manage authentication, logging, and cross-cutting concerns. Middleware components can be plugged in to handle essential tasks such as authentication, authorization, rate limiting, request logging, metrics collection, and header management, all before the request reaches the service. Thus, duplicated logic is reduced across services for consistent policy enforcement.

With API communication in place, it’s time to look at how to handle data across distributed services in a consistent, scalable way.

Step 6: Data Management Strategies

Typically, monolithic applications have general databases that are monolithic too. Having a single database for every microservice is one of the tenets of a microservices architecture. So, in transition to microservices in the process of .NET migration, you must divide the monolithic database according to the service boundaries you established earlier.

• Analyze the Database Mappings: To decide where to separate a monolithic database. The tools like SchemaCrawler, SchemaSpy, and ERBuilder can be handy in that. The same method may be applied to mapping tables or other database objects. However, if a separation between database objects is not clear, rely on other considerations, like latency, joins, transactional integrity, and data synchronization.
• Implement DB per Service: To guarantee loose coupling, autonomous scaling, and fault isolation, each microservice should have its own database. A product service with a lot of traffic, for instance, can grow its database without impacting other services. Additionally, this permits autonomous deployments and facilitates polyglot persistence with the use of tools like as Flyway or EF Core Migrations.
• Put an Event-Driven Architecture: Direct database access across services causes problems with data integrity and tight coupling. Instead, exchange data through events. A service broadcasts an event (such as OrderCreated, InventoryUpdated) when it completes an operation, such as placing an order or updating inventory, allowing other services to respond appropriately.
• Use Command Query Responsibility Segregation (CQRS): Optimize performance, scalability, and maintainability by separating read and write processes. In traditional monolithic systems, the same data model is often used for both reading and writing, which can lead to performance bottlenecks and unnecessary complexity. With CQRS, commands modify data (e.g., creating, updating, deleting), while queries are used only to read data.
• Use Static Data as Configuration: Country codes and supported currencies are examples of static data. They change slowly. Such static data can be injected into a microservice as a configuration with configuration servers, key-value stores, and vaults.
• Replicate Data: Replicating data in the dependent service database is another method of data sharing between two distinct microservices. The data replication can be regenerated at any moment and is read-only, making the service more unified.
• Manage Shared Mutable Data with a Separate Microservice: From a shared mutable state configuration, where multiple modules use a single table, to separate APIs to multiple other services, as shown below.

For instance, the same ShoppingStatus database is used by the e-commerce application’s order, payment, and shipping features to keep track of the customer’s purchase status. You can create a distinct ShoppingStatus microservice to administer the ShoppingStatus database table. As a result, APIs for managing a customer’s shopping status are exposed by this microservice.

Furthermore, in monolithic applications, it’s typical to use a SQL join to the table of another module to retrieve necessary data from that module. To get information, an order module uses a product_id foreign key to join an order to the products table.

However, we advise against having the order service call the product service’s database directly to do a join operation if you dismantle modules as separate services. Instead, an order module uses an API call to get data from a product module is a good alternative.

Despite some performance issues, sharing data through an API works fine with limited data size. Additionally, you can reduce network calls to the called service by implementing a local TTL cache on the caller if the called service is returning data with a known rate of change.

Step 7: Deploy and Orchestrate with Kubernetes

The next step in .NET migration is to effectively manage and operate microservices at scale. To automate deployment, scaling, service discovery, and self-healing throughout your distributed architecture, Kubernetes offers the orchestration layer. Let’s define the techniques:

• Container Orchestration: Automate rollouts, handle restarts, scale services according to demand, and manage containerized services with Kubernetes.
• Service Discovery: Make use of Kubernetes’ integrated load balancing and DNS to enable services to communicate without hardcoded IPs or ports.
• CI/CD Pipelines: To automate build, test, and deployment processes, integrate Kubernetes with CI/CD technologies such as GitHub Actions or Azure DevOps.

We guarantee high availability, fewer manual tasks, and a solid basis for running microservices at scale via Kubernetes.

Step 8: Monitoring and Logging

Visibility becomes crucial as your system transitions to a distributed microservices architecture in .NET migration. Without adequate monitoring, it can be very difficult to spot performance problems or failures when several services are operating separately. Strong logging, tracing, and alerting are therefore crucial. There are several tips on how to tune the process right:

• Centralized Logging: Gather, store, and examine logs from all services in one location by using tools like Azure Monitor or the ELK Stack (Elasticsearch, Logstash, Kibana).
• Distributed Tracing: To identify delays or errors in intricate call chains, use OpenTelemetry or Application Insights to track requests as they move between several services.
• Measures and Alerts: To identify irregularities before they have an impact on users, set up real-time measures (CPU, memory, and reaction time) and set up alerts.

As a result, you may proactively identify problems, minimize downtime, and consistently increase the dependability of your microservices system by building a solid observability basis.

Step 9: Testing Strategies

When switching from a monolithic system to microservices, testing becomes more difficult but also more important. A layered approach to validation is necessary to ensure reliability because services function independently and communicate via APIs. We’d like to remind the process as follows:

• Unit Testing: To identify problems early and make sure internal components operate as intended, test separated functionality within distinct services.
• Integration Testing: By mimicking actual operations and data transfers, you may confirm that several services operate together properly.
• Contract Testing: To assist in picking integration issues during independent deployments, use tools such as Pact to verify that API contracts between services stay constant.

Remember, by combining these tactics, you lower release risk, increase trust in each service, and guarantee seamless cooperation between independently produced components.

Step 10: Adopt an Incremental Migration Approach

A big .NET migration doesn’t have to be a life-or-death situation. On the go with modernization, a staged, incremental strategy lowers risk, increases visibility, and enables teams to constantly produce value. Here’s a conclusion on the most effective strategies:

• Strangle Pattern: Convert monolithic functionality to microservices gradually. The matching monolithic component is “strangled” and decommissioned as each service is finished.
• Feature Flags: Turn features on or off to safely test new microservices in production. This enables controlled rollbacks in case they are required and permits validation without complete rollout.
• Continuous Refactoring: To facilitate future migrations, continuously simplify and clean up the remaining core as services are migrated out of the monolith.

Thanks to these techniques, you minimize disturbance, obtain feedback early, and preserve system stability by modernizing in phases, all the while confidently pursuing a microservices-first architecture.

Challenges of Migrating to Microservices

Sometimes, despite the best effort, something goes wrong in the .NET migration. This section provides a comprehensive way to troubleshoot the most common pitfalls.

Tips for a Stress-Free Migration

Some tips and tricks haven’t been included in the guide body, so this section will examine the additional practices and successful strategies. So that your .NET migration is not only feasible but also genuinely effective.

• Begin Small: Start with non-essential services before moving on to core features.
• Automate Every Task: Automate testing, deployments, and monitoring to cut down on errors and manual intervention. Or apply the latest AI-powered techniques for legacy projects for acceleration.
• Adopt a DevOps Culture: To increase productivity and streamline procedures, encourage cooperation between the development and operations teams.
• Set Priorities in Communication: To prevent miscommunications, ensure that teams working on various microservices communicate clearly and consistently.
• Underscore Domain-Driven Design: To improve clarity and maintainability, use DDD to match microservices with business capabilities.
• Prioritize Security: Use thorough security procedures, such as encryption, authorization, and authentication, to safeguard your microservices.
• Leverage Cloud Services: To make the deployment, scalability, and management of your microservices easier, make use of cloud-native services and tools.

Following these practices, teams reduce friction and ensure their .NET migration delivers long-term, scalable results.

Brief Conclusion

Using .NET to refactor a monolith into microservices is like chipping away at the rock, a strategic change. In addition to gaining agility and scalability, carefully disassembling your old system paves the way for cloud-native operations and AI integration. .NET Migration services from Devox Software are your chance to migrate with the highest .NET migration rates, completely predicted and stress-free.

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