Microservices: What are they? and How Do they Work?

The adoption of microservice architecture has revolutionized the development of cloud applications, allowing for greater flexibility, agility, scalability, and resilience in their design and deployment through the use of microservices. As such, they have become an important approach to software development, especially in cloud and DevOps environments. Today, large internet companies such as Amazon, CrowdStrike, Google, Netflix, PayPal, Twitter, Uber, and Zoom, all use systems that compose numerous independent and interoperable microservices.

Microservices are small, loosely coupled, and reusable software components that usually perform a specific business capability or functionality. This is a software development approach where large systems are built by combining smaller, independent microservices, communicating via well-defined APIs.

Dgtl Infra provides an in-depth overview of the microservices paradigm, explaining what microservices are, their differences from monolithic architecture, and how they are developed and deployed. We also explore the main advantages and disadvantages of microservices to assist organizations in determining if they are the best option for their needs. Finally, we highlight the relevance of microservices in cloud-native applications.

What are Microservices?

The widespread adoption of microservices is closely linked to the rise of cloud computing and DevOps methodology. Microservices are perfect for building distributed systems as they break down complex, monolithic applications into several smaller components or services that can be developed and deployed independently across different servers, and even data centers, as occurs in cloud computing environments.

The microservices architectural style decomposes an application into a collection of services, that perform a single function or a set of functions, needed for a specific business capability. Each microservice runs its own processes and uses lightweight mechanisms, such as HTTP or messaging protocols, for communicating with other services. They can be designed to collaborate and work together to perform complex business operations.

Each microservice can be developed, deployed, and scaled independently of the other services in the application. This allows teams to work on different parts of the application concurrently, deploy changes quickly, and scale only the services that need to be scaled.

As such, each microservice can be owned by a small, cross-functional team, which can work and make decisions independently, allowing for faster decision-making and better collaboration between the development and operations teams, as per the DevOps principles.

Similarly, microservices also align well with serverless architectures and allow granular scalability and control, to magnify agility, scalability, and cost efficiency of serverless computing.

Microservices Architecture

The basic architecture of an individual microservice is quite similar to standard software application architecture – a frontend (or client-side), backend code for business logic, and some form of data storage. The frontend (or client-side) of a microservice differs from standard application frontends because it is only an application programming interface (API) with static endpoints. Well-defined APIs are crucial for allowing microservices to communicate with other microservices, easily and effectively, by sending requests to the relevant API endpoints.

Since a set of microservices work together to form what would otherwise be a single, large application, it is essential to standardize the elements of microservices architecture throughout an organization. This standardization ensures that microservices can interact effectively and efficiently.

Microservices vs Monolithic Architecture

In a traditional monolithic architecture, all of the application logic and data access is contained within a single codebase. This codebase comprises all of the functions and features of the application, which must all be deployed simultaneously, with each server running a complete copy of the entire application.

Over time, it can become increasingly complex to manage and maintain a monolithic application, since each new business decision may require undoing the implementation of previous decisions.

In contrast, a microservice only contains one function, or a small set of functions, for a specific feature and exists in a microservice ecosystem along with other microservices. Each microservice runs its own processes and has access to its own data storage.

Because of this isolation, each microservice can be deployed independently and has its own distinct lifecycle, evolving in its own way, according to changing business requirements. When a component no longer represents the business interest of an organization, it can be swiftly changed without affecting other parts.

Microservices vs Service-Oriented Architecture (SOA)

Microservices are an evolution of service-oriented architecture (SOA), which, similarly, aims to modularize software functionality into reusable services. However, services in SOA are typically larger and encapsulate a significant amount of business logic, as opposed to the more granular microservices. Services in SOA can share resources and coordinate with each other via an enterprise service bus (ESB), which can create a lot of dependencies between services.

On the other hand, microservices are more autonomous and do not share data or other resources. They also do not use ESB, as service-to-service communication is typically handled through lightweight protocols like HTTP and messaging technologies. Overall, microservices overcome the complexity and dependency drawbacks of SOA and are much better-suited to modern cloud-based environments because of their greater isolation, granular scalability, agility, and simplicity.

Example of a Microservices Application

The majority of modern applications and services can be decomposed into smaller components to facilitate a microservices architecture. For example, an e-commerce application can include multiple microservices, such as a shopping cart service, catalog service, user profile and user session services, payment gateway service, order management service, and inventory management service, amongst others. Moreover, each of these microservices can run in its own container – a self-contained, executable unit of software.

Traditionally, an e-commerce application would package all of these various functions together in a monolithic application that would run on a single server. Even if the application had multiple executables, all application components would have to run on the same server for the various functions to coordinate and communicate. In this case, the inter-process communication is instant, but the server also becomes a single point of failure for the entire application.

Microservices are designed to break down this tight coupling of software components to physical hardware. By doing so, different parts of the same application can run independently on different servers, adding resiliency and fault tolerance. Moreover, microservices enable granular scalability and resource optimization, as individual microservices can be scaled up or down according to the specific needs of the application. This simplifies complex applications and improves their performance, since microservices can be tailored to specific tasks and requirements.

Development and Deployment of Microservices

To build, deploy, and manage microservices easily and efficiently, developers follow several development and deployment practices. In particular, containers and APIs have become essential tools for microservices architecture:

Containers and Microservices

Containers have emerged as the de facto standard for hosting microservices because they enable developers to isolate a service within its own environment. Also, containers ensure portability, meaning that services run correctly when moved between different computing environments. The source code, its dependencies, and runtime are all packed within a container image, which can then be pulled and executed on any host.

Microservices packaged within containers can be managed through orchestration services like Kubernetes. Combining microservices with Kubernetes can help organizations optimize their environment for the cloud. This combination allows organizations to manage and scale their microservices effectively through features, such as auto-scaling, auto-healing, and self-recovery.

READ MORE: Containers – What are they? and How Do they Work?

APIs and Microservices

In highly distributed environments, the ability to communicate between microservices is critical. The inter-process communication mechanisms used with microservices are different from traditional applications because microservices are more granular, independent, and loosely coupled.

In a traditional monolithic application, different components typically communicate through direct method calls or shared memory. This creates tight coupling between components, making it difficult to modify one component without affecting the others.

Conversely, microservices communicate with each other through lightweight, asynchronous mechanisms, such as RESTful APIs, message queues, and event-driven architectures. Typically, microservices make their functions available through a set of APIs that can be used by other services to retrieve data or perform actions.

Other Development and Deployment Tools

APIs and containers are crucial elements in microservices architecture, allowing for flexible and modular application development and deployment. However, there are several other important tools that play a critical role in managing and optimizing microservices, which include:

• Service Discovery: tools that enable microservices to locate and communicate with each other, ensuring that they work together seamlessly
• Service Orchestration: tools that automate the management and coordination of microservices, making it easier to deploy and scale them across different servers or data centers
• Logging and Monitoring: tools that help developers track the performance and health of microservices, enabling them to identify and fix issues quickly

Advantages and Disadvantages of Microservices

Microservices have both advantages and disadvantages that can help organizations determine if this software development approach is the best fit for their requirements.

Advantages of Microservices

The advantages of microservices are simplified development, flexible upgrades, granular scalability, fault isolation, reusability, and being technology agnostic.

1) Simplified Development

Each microservice is designed to optimally perform a very specific and limited functionality. This simplifies the development process, as small development teams can focus on individual and narrowly-defined functions. Ensuring effective coordination between independent services can become complex, but a service mesh layer (used in conjunction with microservices architecture) can manage all service-to-service communications without the developers having to define that logic within individual services.

2) Flexible Upgrades

Upgrading services or adding new functionality to an existing application is much easier with microservices, as compared to complex, tightly coupled monolithic applications. Specifically, this architecture enables the addition of new features or the instantaneous updating, patching, replacement, or substitution of microservices within a complex, live application without disrupting the entire system.

3) Granular Scalability

Microservices architecture makes it simpler to deploy additional instances of a particular service across multiple servers and different infrastructure as demand grows. In comparison, monolithic applications do not allow each component to be scaled individually due to tight dependencies.

4) Fault Isolation

Each microservice is completely independent and has its own resources, including data storage. This ensures that any issues or faults that arise are confined to the particular microservice and do not propagate to other services and bring down the entire system.

5) Reusability

Microservices are designed to be reusable, which means that developers can use existing microservices for specific functions or capabilities, instead of creating new ones from scratch every time. Since microservices are fully tested and validated, developers can assume the integrity of the new application without the need for continual testing.

6) Technology Agnostic

Microservices are platform- and technology-agnostic, which means that they can be developed using any framework and coded using any programming language suitable for the type of workload. A microservice can be attached to any suitable data storage system, such as a virtualized drive, blob storage in a bucket, or a database. Being platform-agnostic, microservices can run across hosts and environments.

Disadvantages of Microservices

The disadvantages of microservices are their inherent complexity, the fact that they are a distributed system, and cost.

1) Complexity

On one hand, microservices simplify development with a smaller codebase and independent deployment and testing. On the other hand, they can add complexity, as they require careful planning and design to ensure that the system works seamlessly as a whole. They also require some organizational changes, as each live microservice needs to be actively owned by a team. This often requires significant changes to team structure, development processes, and communication patterns.

2) Distributed System

While microservices offer various benefits in terms of scalability, fault tolerance, and resilience, they also introduce additional challenges in terms of management and maintenance, due to the distributed nature of these systems.

Communication between microservices running within a distributed system is critical and network latency can become a problem. Microservices are large, complex distributed systems with many small, independent pieces that are constantly changing. Individual components can often fail in unpredictable ways.

3) Cost

Organizations have finite resources, whether it be engineering resources or hardware and infrastructure resources. Microservices will compete for resources in a microservices ecosystem, and resources cost money. Typically, microservices will cost more, as compared to monolithic applications, as they need more infrastructure, tools, and expertise. Despite all the benefits of microservices, organizations must weigh the cost of deployment and management before deciding if microservices are a good fit for their particular systems or applications.

Cloud-Native Applications and Microservices

The rise of cloud computing has prompted software developers to re-architect applications to better benefit from the cloud’s elasticity. The primary benefit of microservices architecture is that each component can be deployed and scaled individually. Combining autonomous, platform-agnostic, and independently scalable microservices with on-demand, pay-per-use models of cloud computing can yield significant cost benefits for organizations leveraging a cloud-native approach.

A cloud-native approach refers to a method of designing and building applications optimized for deployment in cloud environments. Typically, cloud-native applications are built using modern software development technologies and practices, such as microservices architecture, containers, container orchestration, and DevOps automation.

Cloud-native applications are built as a collection of multiple independent microservices and utilize containers as an immutable infrastructure and optimal runtime for microservices. Each part of a cloud-native application is housed within its own container and dynamically orchestrated via container orchestration platforms, such as Kubernetes, to optimize how resources are utilized.

READ MORE: Cloud-Native – What is it? and How Does it Work?

Additionally, cloud-native applications use service mesh to manage communications between microservices and API gateways. This helps manage APIs and provides additional security and authentication features, especially as the number of services within an application grows.

Success of microservices will depend largely on choosing the approach for the right applications and systems. Microservices complement systems with high flexibility, scalability, and adaptability needs, such as e-commerce, social media, and online gaming platforms. Conversely, small applications with low traffic, legacy systems, or applications that require real-time communication between components, may benefit from other architectural choices.