Microservice Architecture - Introduction, Challenges & Best Practices

In software development, developers are following different approaches, technologies, architectural patterns, and best practices building the high quality software or the system. Microservice is one of the popular architectural pattern styles followed by the industries. You might have heard this name, and you might have worked on it. 

In a microservice architecture, we break down an application into smaller services. Each of these services fulfills a specific purpose or meets a specific business need for example customer payment management, sending emails, and notifications. In this article, we will discuss the microservice architecture in detail, we will discuss the benefits of using it, and how to start with the microservice architecture. 

What is Microservices Architecture?

In simple words, it's a method of software development, where we break down an application into small, independent, and loosely coupled services. These services are developed, deployed, and maintained by a small team of developers. These services have a separate codebase that is managed by a small team of developers.  

These services are not dependent on each other, so if a team needs to update an existing service, it can be done without rebuilding and redeploying the entire application. Using well-defined APIs, these services can communicate with each other. The internal implementation of these services doesn't get exposed to each other. 

Advantages/Benefits of Microservices

1. Independent Development and Deployment: Each of the services in microservice is deployed independently. As we have discussed that a small team takes the responsibility for these services to build, test and deploy them. This enables faster development. Also, it becomes easy to fix the bug and release the features. You can easily update the service and roll it back if something goes wrong. 

This is one of the best things about microservices, this feature is not available in many traditional applications. If a bug is found in one process or part of the application, then to resolve it, you will have to block the entire release process. 

2. Small Focused Team: To work on a single service, a small team is targeted. Code becomes easy to understand and for new members, it becomes easy to join the team. There is no need to spend weeks figuring out how complex monoliths work. In a large team, it becomes difficult to have proper communication that results in a lack of flexibility. Management time gets increased and agility diminishes.

3. Small CodeBase: In monolithic application code, dependencies become tangled over time. If a developer needs to add some new features, they need to make changes at multiple places. In a microservice architecture, a codebase or database is not shared. Dependency gets minimized, and it becomes easier to add new features. Also, it becomes easier to understand the code and add new features.

4. Mix of Technologies: In a microservices architecture, you're free to choose any technology that suits best for your service. You can mix up multiple technologies and use them for your service.

5. Fault Isolation: In a microservice architecture, you can easily handle critical points of failure. If a service goes down, the functioning of the whole application won't stop, as long as any upstream microservices are designed to handle the failure.

6. Scalability: You break down the application into smaller services and that makes them easy to scale independently. You don't need to scale the entire application. Using an orchestrator such as Kubernetes or service fabric, you can pack the higher density of services onto a single host. Resources are utilized more efficiently.

7. Data Isolation: Schema update is easier to perform because only a single microservice gets affected. Schema update is difficult in a monolithic application. Various parts of the application may touch the same data. Updating the data can make schema risky.

Challenges/ Disadvantages of Microservices

We have discussed the benefits of microservices. Now let's discuss the challenges or disadvantages of it. 

1. Complexity: Services are simpler in microservices, but the whole system is more complicated. You need to take care of all the services and the database, and you need to deploy each of the services independently. 

2. Testing: You need a different approach to write small services that rely on other dependent services. This is different from traditional monolithic or layered applications. Writing tests will be more complex if services will be dependent on each other. To unit test, a dependent service mock must be used. 

3. Data Integrity: Microservice support distributed database architecture. Each service in microservice is responsible for its own data persistence. Data integrity or data consistency can be a challenge in these situations. You may have to update multiple business functions of the application for some business transitions. For different services, you may have to update multiple databases. You will have to set up eventual consistency of data with more complexity.

4. Network Latency: Many small services in Microservice require more interservice communication. If services in microservice will have a long chain of dependencies then additional latency can become a problem for you. You will have to design the APIs carefully. 

5. Versioning: If a service needs to get updated then it shouldn't break the service that depends on it. If multiple services need to be updated at the same time then without careful design you may face some problems with backward or forward compatibility.

Best Practices

1. You can model the services around the business domain

2. We have discussed that individual teams are assigned for specific services, so there is no need to share the code or data schemas. 

3. For each service data storage should be private. You need to use the best storage for each service and data type. 

4. Each service in microservice should communicate through well-designed APIs. Implementation details shouldn't be leaked. 

5. Coupling should be avoided between the services. The coupling has various causes including shared database schemas and rigid communication protocols.

6. You should keep domain knowledge out of the gateway. Routing of client requests should be handled without the knowledge of business rules or domain logic. This should be taken care of very carefully, or you will be facing the coupling problem between the services. 

7. There should be loose coupling and high functional cohesion between the services. Functions that change together should be packaged and deployed together. If the functions reside in separate services then this should end up being tightly coupled. Updating one service requires updating the other service. 

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