One of the most significant shifts in enterprise software today is the move from monolith to microservices. Many see it as the path to agility and scalability, but it’s a transition that can be more complex than it first appears. In this post, we’ll share some of the key challenges and strategies we’ve learned along the way to help you plan your move with confidence.

Breaking Down a Monolith: Where to Start

The first step in moving from a monolith to microservices is understanding what you have. This means creating a clear picture of your current application: how its modules work together, how data flows, and where the dependencies lie. We use tools like static code analyzers, dependency graphs, and architecture design records to get this baseline.

Once you have this picture, look for logical seams in the application. Ask yourself which parts are already loosely connected and could work as separate services. Here are some good places to start:

• Authentication and Authorization: These modules are usually stateless and can be separated easily.
• Email and Notification Services: They’re often event-driven and have minimal impact on core functionality.
• Reporting or Analytics Engines: These typically use replicated data and don’t need real-time integration, so they’re low risk to extract.

By starting with these clear candidates, you avoid disrupting the entire system at once.

Using the Strangler Fig Pattern and Facade APIs

We often use the Strangler Fig pattern when switching from a monolith to microservices. In this approach, new microservices are added next to the existing system. Over time, the monolith becomes smaller as these services take on more work. It’s a safer way to update the system without a risky complete rewrite.

Another helpful technique is the facade API. This wrapper acts as a bridge, letting the monolith and new microservices live side by side. It also makes it easier for your team to manage both legacy and modern code in the same environment.

Managing Inter-Service Communication

Synchronous Communication

Synchronous communication happens when one service calls another directly, usually over HTTP or RPC. It’s simple to understand, but it creates tight coupling. If one service fails, others that depend on it might also break. To handle this risk, you need to include:

• Timeouts
• Circuit breakers
• Retry logic

These help make your services more resilient and reduce the chance of cascading failures.

Asynchronous Communication

With asynchronous communication, you use message brokers like Kafka, RabbitMQ, or Azure Service Bus. This method decouples services, making them easier to scale. But it also adds new tasks like managing event schemas and handling “dead letter” queues.

No matter which communication model you use, you need to plan for failures. Use correlation IDs for tracing so that you can monitor and debug issues across your distributed system.

Avoiding Common Pitfalls in Microservices

One of the biggest risks in moving from monolith to microservices is breaking things apart too fast. If you split every function into its service right away, you create a lot of overhead. More deployments, more monitoring, and more complexity can slow you down instead of speeding you up.

To avoid this, we recommend starting with domain-driven design. Group related features into bounded contexts and let those guide your service boundaries. For example, instead of making five separate services for different parts of user management, start with a single user management service. This reduces complexity and helps your team stay focused.

Tools to Support Your Microservices Transition

Several tools can help you manage your new microservices architecture effectively:

• API Gateways: Tools like Kong or Azure API Management can manage traffic and security for your APIs.
• Service Catalogs: Tools like Backstage let you track your services and keep things organized.
• Observability Tools: Tools like OpenTelemetry and Jaeger help you monitor how everything works together, so you can catch issues before they grow.

The key is to have the right-sized services that align with your team and your business needs.

Key Takeaways for Your Move from Monolith to Microservices

• Start by understanding your current system’s structure and dependencies.
• Use a safe pattern like the strangler fig to replace pieces over time, not all at once.
• Plan your service boundaries with domain-driven design to reduce future complexity.
• Be careful not to split things up too soon; focus on the “right size” for your services.
• Use modern tools to keep everything organized and observable as you grow.

Ready to Get Started? Let’s Talk

Moving from monolith to microservices isn’t just about technology. It’s a complete shift in how your team builds and maintains software. At Keyhole Software, we’ve helped many clients plan and execute these transitions without unnecessary complexity or risk. If you’re exploring this move, reach out to us for a free consultation. We’d be happy to help you build the future one service at a time.