Monolithic & Microservice Architectures

The appeal of a microservices architecture is undeniable. Microservices are highly scalable and resilient platforms that can maintain high throughput even if some of their partner services experience outages. The well-documented benefits of this architecture can, at times, result in extreme complexity in maintaining and extending the platform.

Moving away from the monolithic architectures of the past is a natural trend, and while the benefits are significant, building out these systems requires a considerable amount of work. These systems need to be designed with careful attention to maintaining the separation of concerns between each microservice and ensuring that the service is loosely coupled from the overall solution.

I will try my best to decompose some of the challenges I have personally faced with the build out of a finance-based system.

Operational Overhead and Cost

A microservices architecture is highly distributed and independent, which requires the development or purchase of specialized tools to manage and support the infrastructure. However, having an entire DevOps team equipped with these tools can become expensive. In comparison, monolithic platforms are more easily managed and maintained with a smaller team.

Data Consistency

In a microservices architecture, each microservice has its own data source that is not shared with other services. If a data source is coupled to multiple microservices, a shared dependency is created, which can lead to issues with all microservices using the service in the event of a failure.

However, when multiple microservices use the same or similar information, data consistency can become a potential issue. Attempting to create and maintain consistent data across multiple services can be challenging and time-consuming, and inconsistent data can lead to serious issues. While there are several strategies to avoid data inconsistency, the implementation considerations can be complex and require careful attention.

Testing Challenges

In a monolithic architecture, testing is relatively simple, and it involves ensuring high unit test coverage for each module and testing the entire system to ensure end-to-end flows remain functional after each modification. However, with a microservice platform, testing becomes more complex. It requires unit testing for each microservice, testing microservices as a whole, testing end-to-end flows by coordinating calls via automated testing platforms, performing API contract testing, and using service virtualization.

This complexity is due to the distributed nature of the system, and the need to test each microservice independently as well as collectively. In addition to unit testing and testing the system as a whole, testing requirements for microservices architecture can also include service discovery and registration, versioning, routing, and load balancing. Furthermore, API contract testing and service virtualization can be necessary to ensure consistency and compatibility between microservices.