When to choose a Microservice over a Monolithic application
Published: 2024-01-22 23:39:58

From research, many projects initially start as a monolith and then evolve into a microservice architecture. Oh, for clarity’s sake, let’s explain what a monolith and a microservice mean. 

Imagine a building, grand and sturdy, at the heart of your town. This is your monolithic software. For a while, it serves everyone's needs, but as years pass, more residents flock in, craving new shops and services. Suddenly, the grand building feels cramped. Adding on becomes a messy patchwork, confusing everyone. 

Now, envision a vibrant market square, each stall a vibrant microservice! Customers easily find what they need, and new vendors can set up shop quickly. This is the potential of microservices- (agility and growth without chaos). 

Sure, the old building served well, and tearing it down is no small feat. But for thriving towns, a bustling market might be the answer. As demands grow, microservices can respond dynamically, keeping everyone happy. With this example, let's dive into what a Monolithic and Microservice Application is.

**What is a Monolithic Application?**

![Monolithic Service Image](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/f3ddniqn7ynlepz4zdab.png)
Monolithic application is a traditional method of software development, it is a plain straightforward architectural pattern for developing a complete application as a single unit. A typical monolithic application consists of the User Interface, Business Logic, Data Layer, and Database.  
A monolithic application follows some principles, here are a few.

- Shared data: All components share the same data repository simplifying data management and ensuring consistency. 

- Streamlined development: Building and deploying the application is often simpler due to the absence of interactions between separate services. 

- Unified structure: All functions are integrated within a single codebase, creating a tightly interconnected system. 

- Focused governance: Centralized control of the codebase can enhance manageability, especially for smaller teams.  

## **Advantages of Monolithic Application**


**Streamlined development and deployment:** 

- Single codebase: A unified codebase simplifies development, testing, and deployment processes. 

- Centralized structure: The application's centralized nature enables efficient end-to-end testing and debugging. 

- Horizontal scalability: Running multiple copies behind a load balancer provides horizontal scaling capabilities. 

**Performance:**

- Centralized API: A centralized codebase can potentially enhance performance by reducing the overhead associated with multiple APIs. 

**Ease of use:**

- Straightforward deployment: Deployment often involves simply copying the packaged application to a server. 

## **Disadvantages of Monolithic Application**

**Large and complex systems:** 

- Development: Monoliths become difficult to understand and modify as they grow, slowing down development speed. 

- Scalability: You can't scale individual components, requiring scaling the entire application, which can be inefficient. 

- Start-up and deployment: Large size can lead to slow start-up times and require full redeployment for even small changes. 

**Fragility and inflexibility:**

- Reliability: A single bug in any module can bring down the entire application, impacting availability. 

- Testing: Complex changes require extensive manual testing due to poorly understood impact. 

- Continuous deployment: Difficulty of deploying updates frequently due to redeployment overhead. 

- Technology adoption: Changing frameworks or languages is expensive and time-consuming across the whole application. 

In essence, monolithic architecture's simplicity shines for smaller projects, but its inflexibility and fragility become major drawbacks as applications grow and complexity. 

**What is a Microservice Application?**

![Microservice Image] (https://dev-to-uploads.s3.amazonaws.com/uploads/articles/ggssi0vfij22xie5z0u2.png)

Microservices architecture breaks down applications into independent, bite-sized services (like mini-apps). Each service owns its specific functionality, data, and deployment, making them modular and flexible.

**Advantage of Microservice**

- Scalability: Need more power for a specific feature? Scale that service alone, without affecting others. 

- Resilience: A problem in one service won't crash the entire app. Think isolated fires, not infernos. 

- Innovation: Different teams can own different services, boosting development speed and flexibility 

- Agility: Update, test, and deploy features on the fly, one service at a time. No need to rebuild the whole app. 

- They communicate through well-defined APIs: REST, RPC, messages, or even carrier pigeons (don't judge). 

## **Disadvantage of Microservice**
**Distributed System Headaches:**

- Communication: Choosing and implementing how services talk to each other (messaging vs. RPC) adds overhead. 

- Failure Management: Dealing with partial failures and other distributed system quirks requires extra code and planning. 

**Data Challenges:** 

- Fragmented Data: Splitting databases across services can make transactions involving multiple entities complex. 

- Consistency Trade-offs: Eventual consistency, while efficient, can be tricky to manage and can lead to data inconsistencies. 

**Testing Hurdles:**

- Dependency Chains: Testing a single service often requires launching its dependencies, making it cumbersome and time-consuming. 

- Coordinated Rollouts: Changing multiple services requires careful planning and synchronization, adding complexity to deployments. 

A Microservice application also follows some principles but will mention a few.  

- Single Responsibility: Each service should handle a single, well-defined task. No multitasking is allowed. 

- Automation for Efficiency: Streamline processes like testing and deployment to save time and reduce errors. 

- Observability: Track each service's health and performance to spot issues early, like a fitness tracker. 

- Continuous Integration and Deployment (CI/CD): Adopt CI/CD practices for frequent and seamless updates, like a well-oiled machine. 

- Discoverability: Services should be discoverable, like having a map of a new city. 

Remember: Microservices are not a one-size-fits-all solution. Weigh the benefits of agility and scalability against the increased complexity before adopting them for your project. 

Choosing the right architecture is crucial for building successful applications. While both approaches have their merits, their strengths cater to different needs: 

Monoliths are Simple but Strong, However, for complex applications, monoliths become cumbersome. Microservices are Agile and Resilient, but microservices come with their own challenges. 
 Ultimately, choose the architecture that best empowers your project based on its complexity, growth potential, and desired agility.