Guide - Software Architecture: Monoliths vs Microservices
- Type
- Guide
- Year
- Category
- Containers, Serverless, Software Architecture, Monoliths, Microservices
The choice between a monolithic application and a microservices architecture is highly contextual and depends on various parameters, including the application requirements, team skills, and overall customer experience. Let's explore the nuances of both approaches and how one might decide between them based on specific considerations.
Monolithic Application
A monolithic application is a single-tiered software application where the user interface and data access code are combined into a single program (single process) from a single platform. It's a traditional model of software architecture that has its advantages and disadvantages. For example, a WordPress website or a custom NodeJS application combined with React or Angular and running as a single process.
Advantages:
- Simplicity: Easier to develop, deploy, and manage due to its single-tiered nature. All the features are part of a single application and the code is also structured similarly.
- Development Speed: Initially, it can be faster to develop because you're dealing with a single codebase.
- Testing Ease: Testing can be more straightforward since you're dealing with one integrated set of components.
- Deployment Ease: Rolling out new changes is fairly straightforward, everything will go in a single bunch.
Disadvantages:
- Scalability Issues: As the application grows, scaling specific functions or components can become challenging. As the entire application runs as a single process, horizontal scaling is the only option.
- Technology Stack Lock-in: You're generally more locked into the technology stack you initially chose. Given the earlier example of WordPress or a custom NodeJS/Angular application, it's hard to change the underlying platform.
- Long-term Complexity: As the application evolves, the complexity of the codebase can lead to slower development speeds and increased risk of bugs.
- Deployment: As the entire application will be deployed as a single unit, all the changes has to be coordinated accordingly. This can increase the deployment time.
- Single point of Failure: This is quite obvious fallback. As your entire application is running as a single process, failure in any part can bring down the whole application. Even if you change a code in a less critical part of the application, it can still affect the whole application.
- Cost of Scaling: Large monolith applications are both difficult and expensive to scale because you need to scale the whole application. This is the actual infliction point where teams start extracting the features and building smaller services, and slowly transitioning into microservices.
Microservices Architecture
A microservices architecture consists of a collection of small, independent services. Each service is self-contained and implements a single business capability. There is a possibility that each of these services is using different technology stack and the choice of database.
Advantages:
- Scalability: Easier to scale and update parts of the application without impacting the entire system. As each service runs in an independent process environment, it's easier to manage their resources.
- Technology Diversity: Allows the use of different technology stacks for different components, based on what's best suited for their requirements.
- Resilience: Failure in one service doesn't necessarily bring down the entire system. However, this is easier said than done, as all the dependent services have to accept the failures accordingly.
Disadvantages:
- Complexity in Deployment and Management: Requires more effort in terms of infrastructure orchestration, networking, and data consistency. Using microservices for simple use cases is a very typical oversight, leads to unnecessary complexities and operational overhead.
- Development Overhead: Initially, it might slow down development because of the need to set up communication between services, as well as dealing with distributed data management. This will require additional overhead of creating fine-grained service boundaries.
- Operational Overhead: As each service runs in separate process space, uses different platforms, and different databases - overall it requires a robust infrastructure for monitoring, logging, and ensuring security across services.
- Deployment overhead: Because you have multiple source projects, you have to ensure the packaging and deployment mechanism accordingly for each of the services. Also, as each service can effectively communicate other services, the infrastructure will also require a mechanism for service discovery or service endpoints.
- Cost of Distribution: Each service will require it's own set of compute, storage and networking resources. If not well optimized, this can quickly add up the overall cost of running the entire application. Plus the overhead cost for monitoring, logging and other infrastructure activities. This is the infliction point where teams start merging some the features and redefine services boundaries to reduce the management and operational overhead.
How to Decide
When deciding between a monolithic architecture and microservices, consider the following parameters:
- Project Size and Complexity: Small projects with a clear scope and predictable user base might benefit from the simplicity of a monolithic architecture. Large, complex projects or projects that are expected to evolve over time might be better served by microservices.
- Team Expertise: If your team is experienced with microservices and distributed systems, they might navigate the complexities of microservices more effectively. They are well aware of the pros and cons of each and will be able to make informed decision based on the use case. ALWAYS CONSULT your team.
- Scalability and Performance Needs: If you anticipate needing to scale parts of your application independently or have high demands for performance and availability, microservices might be the way to go. This is sometimes easy to understand upfront, or may evolve with time. Imagine some features of your application became very popular, so you can evolve those over time. Snap (Snapchat) was originally a monolithic application running on Google App Engine.
- Technology Diversity: If different components of your application would benefit significantly from different technology stacks, microservices allow that flexibility. This highly depends on the use case, for example processing thousands of requests in small time requires an optimized framework, using specific tools and framework for video/image processing, etc.
- Long-term Vision: Consider not just the immediate needs but the potential evolution of your application. A monolithic architecture might be quicker to launch but could become a bottleneck as your application grows. However, many teams prefer this option especially in the Startup category, as they want to first validate the idea quickly before investing a lot on the technology side.
Ultimately, there's no one-size-fits-all architecture. The decision should be based on a thorough analysis of your specific context, considering both the current state and future goals of your application.
Transitioning between architectures is possible but comes with its own set of challenges, so making an informed initial choice is crucial.