What Is Microservices Architecture? (+The Why and How)

Did you know why Netflix migrated from monolithic to microservices architecture? To scale. 

As one of the first big companies to transition from monolithic to microservice architecture, Netflix needed a way to remain agile in managing the rapid growth of its user base. By adopting microservices architecture, they scaled each service independently without interrupting the high-demand video streaming service. 

These services communicate using hypertext transfer protocol (HTTP), message queue, and various other ways. Even if any service fails, it doesn’t crash the system, making it more reliable for its uptime. When a service experiences heavy traffic, it scales up without affecting others.

But what exactly is microservices architecture, and what makes it different from the traditional monolithic approach? Let’s dive in.

This separation of services allows teams to deploy, fix bugs, and modify features without causing much disruption as the changes are made to independent services. What’s more, microservices architecture helps improve scalability and resilience, encouraging teams to align with DevOps practices to ensure continuous delivery and agile workflow.

Spotify is another famous company that uses a microservices architecture for efficiency and resilience. Since each service is designed to function independently, developers work on it simultaneously to test and update the application. For example, if Spotify's recommendation service goes down, users can still stream music without interruptions.

Microservices architecture encourages simultaneous development and testing of services but requires tools to facilitate effective coordination. It increases application development speed by breaking up an application into smaller components, similar to how service-oriented architecture breaks up monolithic applications into smaller parts. However, their approaches are different.

Microservices architecture would work well in situations where:

• A website hosted on a monolithic platform is being migrated to a cloud-based and container-based microservices platform. 
• Images or video assets (stored in an object storage system) are served directly to mobile or web.
• Invoice services need to be separate from payment processing and ordering. If invoicing isn’t working, the system will still accept the payments. 

Microservices components

Here’s an overview of what a microservices architecture looks like with its components aligned: 

Source: Microservices

Take a look at the different components of the above diagram and what they do: 

• Account services/ inventory services: These represent individual microservices that hold specific responsibilities for specific functionality. They’re loosely coupled and communicate with the network.
• Application programming interface (API) gateway: The API gateway acts as a single entry point for clients, routing requests to specific microservices. It manages activities like load balancing, rate limiting, and authentication.
• Service registry: This saves all the relevant information regarding the location and availability of microservices. Service registry makes it easier for services to connect, allowing dynamic scaling and routing.
• Load balancer: It administers traffic through multiple instances of a service, improving its performance and availability.
• Database: Each service has its database to facilitate data autonomy and reduce dependencies.
• Interservice communication: Communication happens over lightweight protocols like representational state transfer (REST)/HTTP or remote procedure calls (gRPC), which allows data to flow between services.

Microservices communication methods 

Microservices use two main communication methods, each with its own use case and advantages. Here’s a breakdown of the types:

Synchronous communication 

In synchronous communication, the client sends a request and waits for a response from the service, temporarily blocking its operations until a response is received. Similar to a telephone call, the conversation only continues if both parties are present.

Synchronous communication is typically done using:

• HTTP/HTTPS protocols: These are commonly used in REST APIs, where clients make requests like GET, POST, or PUT, and services respond with JSON data.
• gRPC protocol: An alternative to REST, gRPC is faster and more efficient because it uses binary data rather than text. Although it requires clients and services to support its format.

REST APIs are used for client applications on the web or mobile that need an immediate response. For internal services, gRPC helps prioritize speed over readability. 

Asynchronous communication 

In asynchronous communication, the client sends a request but doesn’t wait for a response. As with sending a text message, the client can continue working without waiting for a response.

Asynchronous communication relies on:

• Message brokers: Protocols like advanced message queuing protocol (AMQP) allow services to communicate through brokers like Kafka or RabbitMQ, where messages are stored in queues until they are processed.
• Queue and topic modes: Asynchronous communication can operate in one-to-one (queue) mode, where a single message is sent to one receiver, or one-to-many (topic) mode, where multiple receivers can process the message.

Async communication is suitable for systems with event-driven architectures, such as e-commerce applications with separate services for order creation, payment processing, and shipment. It suits applications where individual services don’t rely on immediate feedback. 

How communication occurs in an e-commerce application 

In an e-commerce application, both synchronous and asynchronous communication takes place simultaneously. For example, when a client submits an order, REST API handles this to confirm the receipt immediately. 

On the other hand, the payment service processes the payment in the background without holding up the client’s shopping experience. This is done through async communication. 

Typically, RESTful APIs with HTTP are preferred, whereas JavaScript Object Notation (JSON) responses are easy to read and debug, especially in public-facing APIs.  Internally, gRPC facilitates customer and order-related services in the microservice environment to achieve high-speed communication. 

Microservices architecture vs. monolithic architecture 

Every service in a microservices architecture has its business logic and a database, making it easier to update, test, deploy, or scale within the service. Microservices have independent code bases that allow applications to scale and adapt to new technologies, frameworks, and coding languages. 

While this approach saves developers time when making changes to an application, at the same time, it increases the complexity of managing services. 

In such instances, development sprawl occurs when development happens in a scattered and discontinuous manner. Without effective management, this might slow the development speed or affect operational performance. As more microservices are added over time, it can become difficult to identify what services your team can utilize and who you would contact for support. 

However, microservices architecture promotes an agile working method that allows developers to deploy continuously. Suppose a service reaches load capability, to combat it, you can deploy additional instances of that service to relieve the pressure. It becomes easy to add new technologies and ensure the application won’t go down after deployment. 

Source: Atlassian

A monolithic architecture, on the other hand, has a simpler design. Ai single code base houses business applications. Any update in the application’s functionality means updating the entire code and verifying the updated version doesn’t bring the application down. This makes any updates restrictive and a lot more time-consuming. 

Monoliths are okay when you’re in the early stages of product development. They might help reduce cognitive overhead and manage code easily, enabling developers to deploy faster and all at once. However, they are not scalable or flexible enough to adapt to new technologies and frameworks on the market. 

Moreover, if any error slips past you, a monolithic architecture has the potential to disrupt the application’s availability. 

Since monolithic and microservices architectures serve different purposes, businesses might transition to microservices to keep up with the scalability and flexibility of their systems.

Microservices vs. service-oriented architecture (SOA)

Microservices and SOA organize software into independent services. The difference lies in flexibility, design principles, and scalability. SOA primarily caters to enterprise use cases where services can be reused while ensuring application interoperability. Its modular design lets businesses scale services independently and manage varying traffic loads without disruption. 

However, integrating SOA’s large service blocks can be tricky, especially if they’re built with different technology. 

On the other hand, microservices adopt a more granular approach. They break down the software into components that handle specific business functions. This makes the application more flexible to scale, and any fault within a service can be easily contained. Microservices typically run in containers (Docker, Kubernetes, etc.), enabling highly efficient deployments.

SOA and microservices require different deployment strategies, but both benefit from DevOps practices:

• SOA: Typically, it involves deploying the entire application as a single unit. This requires careful coordination and can be time-consuming, especially for large applications. DevOps practices like automated testing and configuration management help reduce errors in SOA deployments.
• Microservice:L This type of deployment supports more granular deployments, allowing each microservice to be deployed independently. Continuous integration and delivery (CI/CD) are essential here, enabling rapid and frequent releases by automating testing, building, and deployment processes.

Organizations often use both SOA and microservices to create hybrid systems, using SOA for legacy components and adopting microservices for new features. 

SOA is best for large, complex enterprises that focus on reusability and interoperability. Microservices are better for companies that prioritize speed and agility, often in environments with a DevOps culture focused on continuous delivery.

Use cases of microservices architecture 

As we discussed, Netflix is one of the most notable success stories when it comes to microservices architecture. They took a bold gamble back when the structure of microservices wasn’t that well known. 

Although it allowed Netflix to handle real-time video streaming for a growing global audience, this architecture is still ambiguous.

On one side, it’s a disruptive solution to monolithic architecture's flexibility and scalability challenges. On the flip side, it can slow down the development with the increased complexity of integration and testing.

Still, microservice architecture is preferred for the following use cases, including:

• Apps that use big data, artificial intelligence (AI), or machine learning. Big data requires complex data pipelines, such as one pipeline for collection, another for processing, and several for delivery and storage. As it’s loosely coupled, it automatically becomes a good fit for microservices. 

• Moving from legacy systems to the cloud. When organizations move to the cloud or conduct global system modernization, they rebuild their IT capabilities using microservices architecture to make their apps more scalable and flexible. 

• Real-time data processing. Any application that requires real-time processing data, such as streaming services and online booking platforms, uses microservices to deliver faster output and manage the incoming traffic load. 

• Large-scale systems with complex logic. Third-party applications that other businesses use to offer analytics or monitoring services need more resources. Microservices help them process the data at scale while ensuring they operate with stability and uptime. 

How to transition from monolithic to microservices architecture 

It’s common to find several projects that start with a monolithic architecture. As the application grows and needs more flexibility, developers often find moving to a microservices architecture rewarding. Below are a few practices to set you up for migration.

The actual process will depend on the system scale and the components in your application. However, there’s some structure to get you started. 

1. Plan the migration 

Determine the service that you would migrate. Analyze your customers' unique profiles and usage patterns to choose the service. Think about which transition can cause the most and least disruption. 

Scalability often motivates businesses to move toward a microservices architecture. Even if you achieve scalability on a rarely used component, its impact would be negligible. Logically, you should prioritize heavily used components and migrate them first. 

Users expect their system to return data with a high level of detail, usually as fast as the data is acquired. Such jobs involve multiple data objects and actions. The migration team must consider these factors when switching to a microservices-based system. 

This planning will help you minimize issues and foresee challenges as you shift from a monolith to a microservices-based application. Let’s take a look at the process of migration: 

• Identify the components you want to migrate. Prioritize the components that will migrate from a monolithic to a microservices environment.
• Refactor components to migrate. Check for data accuracy and formatting among different data types to identify outliers or missing data.
• Check dependencies. Identify the application's usage pattern using static analysis of the source code or dynamic analysis tools to find dependencies between components.
• Identify component group. Aggregate components into cohesive groups that can be transformed into microservices.
• Create an API for remote user interface (UI). The remote UI will communicate between the system, the user, and components. This should be both before and after the migration. 

Migrate component groups to macroservices (move component groups to separate projects and make separate deployments). Then, migrate macroservices to microservices. Repeat these steps until complete.

Ideally, you would want to migrate the components that are: 

• Heavily used by most users
• Frequently used
• Least dependent on other components
• Performing slowly

In this step, system architects will ask if two or more applications provide similar data and if they can merge them. They’ll also consider whether different data fields are missing similar objects. 

2. Get the tools right 

Create a service catalog to list and manage different microservices. Before production, automate code checks for better quality, security, and reliability. Use the right tools to gain visibility and monitoring capability during migration. 

You can use a micro-services-specific toolkit to include automated services with built-in monitoring and caching. Automating these aspects reduces errors while delivering real-time insights into migration. 

3. Ensure leadership buy-in 

Strong support from your business's leadership gives you confidence that you can achieve migration success while making tough choices. Make sure the communication is transparent and consistent, and every stakeholder is kept in the loop to convey the migration’s progress. 

As you move forward, keep celebrating the milestones you achieve. This will improve your team’s morale and encourage them to move further with the process, giving them positive reinforcement. 

4. Make the culture shift seamless 

Earlier, the code was supposed to be handed off to the operations team for deployment. Each team will manage development, deployment, and monitoring in a microservices environment. You’ll adopt a DevOps approach that encourages more ownership and accountability in a collaborative environment. 

Gradually, let the teams move toward a culture that values more ownership. This will be pivotal to ensuring the long-term success of the migration. Throughout the process, ensure high reliability and stick to the standard. This will help you avoid service issues while your application’s functional quality doesn’t fluctuate.

Should you migrate or not? 

Migration from monoliths to microservices is a considerable undertaking but has many benefits. Microservices offer greater flexibility and resilience with improved agility. However, not every organization needs to make the switch. Many legacy monoliths work just fine. But, as companies scale and applications grow more complex, the microservices approach helps streamline processes while making applications more scalable. 

The trend toward distributed systems is driving many organizations toward microservices. 

Learn more about how cloud migration software helps companies upgrade their systems.

Edited by Monishka Agrawal