Microservices vs. APIs: What's the difference, and how do they work together?

This post explains the difference between microservices vs. APIs, including their definitions and use cases, technical advantages, and how they work together to deliver online services.

APIs and microservices are two different technologies that serve different purposes: an API is a set of rules and protocols that allow software applications to interact with each other, while a microservice is a self-contained unit of functionality that can be independently deployed and operated. Microservices and APIs are two very different things that are often used together.

What is an API?

An API (application programming interface) is a set of programming instructions that allows software to interact with other software, such as online services or device drivers. Each function provided by an API corresponds to a particular task that needs to be performed (such as retrieving data, performing some processing, or accessing a hardware feature).

APIs can expose any kind of functionality or data. For example, the Google Maps API provides functions for displaying maps and for retrieving directions from Google's online services. This includes data types for representing geographical coordinates and street addresses. APIs are not limited to online services: for example, a mobile app may need to use an API to control a piece of hardware, such as a drone or a robotic arm. 

By using an API, developers can save time and effort by using existing functionality (either from a public API or from their own existing code) rather than having to write their own from scratch. APIs also allow developers to create applications that make use of the functionality provided by the API without having to understand the underlying implementation details. For example, few developers are specialized (or have the resources) to develop their own AI products, but they can readily integrate publicly available AI services via their APIs.

Public and private APIs

APIs can be private and only used for a particular project or within an organization, or publicly available as a free or commercial service.

Private APIs are often used for accessing internal data stores. This data may include sensitive information such as customer records or financial information. By using a private API, developers can ensure that this data is structured and limit access to specific users and groups with more flexibility than giving users direct access to databases.

Developers can access public APIs to integrate other products with their own. Public APIs can also be an important part of an online company’s business strategy by opening up data and functionality to third-party developers, tapping into new markets, and creating new revenue streams.

HTTP API protocols

API protocols govern the way that applications communicate with each other. These protocols determine how to format, transmit, and receive data between two systems.

HTTP APIs allow for data and functionality to be accessed over a network. The most common HTTP API protocols are REST and GraphQL. Each protocol has its own set of advantages and disadvantages. If you’re creating your own API for others to use, it’s important to carefully consider which protocol best suits your needs before building an API.  

HTTP APIs are commonly used to provide data to mobile and web applications. For example, an API server can provide up-to-date weather information that a mobile app can periodically check and display to the user.

REST APIs

REST (representational state transfer) is a standardized architecture for creating APIs for web services. It uses HTTP requests to GET, PUT, POST, and DELETE data to multiple API endpoints, each representing a specific resource.

REST is not a specific technology but rather a set of constraints and principles that ensure scalable and efficient communication between systems. By adhering to these constraints, REST APIs have increased flexibility and maintainability, while remaining simple to implement and consume.

One of the key principles of REST is the separation of client and server responsibilities. The client sends an HTTP request to the server, which then processes the request and sends back an HTTP response containing the requested information or actions taken on the resource. This allows for decoupling between the client and server, allowing for easier implementation and modification of either component in the future.

REST APIs (and GraphQL APIs) can be secured with an API key. Making a request to an API is often referred to as making an API call.

GraphQL APIs

GraphQL is a query language for API development that allows clients to request specific data from a server, giving more flexibility and efficiency compared to traditional REST APIs. It has gained popularity in recent years and is now used by major companies such as Meta (who invented GraphQL), X (formerly Twitter), Shopify, and Contentful.

Instead of multiple endpoint URLs for different types of data, GraphQL uses a single endpoint and allows the client to specify exactly what data they want to retrieve. This eliminates over-fetching or under-fetching of information, as the client only receives the exact data requested.

GraphQL can also be used for real-time updates through subscriptions. This allows clients to receive updates instantly when a change is made on the server side, rather than continuously polling for updates.

While GraphQL is much more powerful than REST APIs, its implementation may not be worth the extra complexity for many use cases where REST is sufficient. Both are popular and powerful tools that suit different use cases.

What are the benefits of using APIs?

APIs are used to allow different software systems to communicate and exchange data with each other. This provides several key advantages.

Ease of integration

By using an API for an existing software solution, you can easily integrate its features into your existing product without having to develop and test them yourself. 

For example, an ecommerce website may use an API to connect to a payment processing system in order to process customer payments. Another common use of APIs is for social media platforms to allow third-party developers access to their platform’s features, such as the ability to automatically post content or pull user profile information.

Well-designed APIs provide a consistent interface regardless of the programming language or platform that is being used. This makes it easy for developers to work with the API, regardless of their background.

Expansion and scalability

Adding new features should not be a time-consuming and difficult process. When building an application, you want to be able to scale quickly and easily to meet the expectations of a growing number of users.

Online platforms that can be integrated using APIs allow you to expand your functionality quickly and to scale, such as major online platforms that provide APIs for accessing their services host them on their own infrastructure, reducing the resources you need to deliver your product as your user base increases.

Automation

Another benefit of using APIs is that they can help to automate tasks.

For example, if you need to retrieve or update data from a remote server regularly, you can write a script to call the API, fetch the necessary data, and store it locally, eliminating the need for manual intervention.  

What are microservices?

Microservices are a type of software architecture that allows developers to build applications as a collection of small, independent services. This approach contrasts with the traditional “monolithic” architecture, in which an application is built as a single, tightly integrated codebase that must be developed and deployed as a single unit.

In a microservices-based architecture, each microservice provides a specific, focused functionality. The application is made up of a number of these microservices, each of which can be called independently when it is needed.

While there can be some additional complexity to their implementation, microservices have become increasingly popular in recent years due to their scalability and resilience.

What are the benefits of microservices?

Microservices offer greater flexibility and scalability compared to monolithic codebases, making them advantageous in many scenarios.

Service independence

There are several benefits of using microservices for service independence:

• Each service can be developed and deployed independently of the others, enabling faster development cycles and greater scalability.

• Microservices can be implemented in different programming languages, making finding the right technology stack for each service easier.

• Each service is self-contained, so it is easier to identify and isolate problems when they occur.

More effective data processing

One of the most important reasons for using microservices is that they allow for more effective data processing. When data is spread out across multiple services, it can be processed in parallel, which can lead to significant performance gains.

Microservices can also be scaled independently so that each service can be sized according to its needs.

Efficiency and flexibility

When applications are broken down into smaller, independent components, it becomes much easier to scale them up or down as needed. For example, let's say you have a monolithic application with dozens of different features. If one of those features becomes popular and starts getting a lot of traffic, the entire application will need to be scaled up to accommodate the increased demand. This would mean paying for the infrastructure to scale the entire application. However, if you're using microservices, you can simply scale up the specific service that's being used most frequently without providing wasted extra capacity for other, less used services. 

Another way that microservices can increase efficiency is by making it easier to roll out updates and new features. With a monolithic application, if you want to add a new feature or update an existing one, you have to deploy the entire application again. This can be a time-consuming and error-prone process. However, with microservices, you can deploy only the service that's been updated, which is usually much quicker and easier.

Microservices can also help improve your team's efficiency by allowing them to work on different parts of the system concurrently. Each team or team member can work independently on their own service, and then those changes can be deployed separately. This means that you can get new features and updates out to your users much faster.

Stability and resilience

Well-designed, microservices-based applications can be more stable. Since each microservice is self-contained, if one service goes down, the rest of the application can continue to function normally. This is in contrast to a monolithic architecture, where a single failure can bring down the entire application.

Another benefit of microservices is that they promote resilience. When an application is built using microservices, it can be more easily replicated across multiple servers. This provides increased availability in the event of a server failure. Additionally, microservices can be deployed in different regions, providing protection against outages that might occur in a single location, and improving responsiveness by executing code and delivering data from servers located closer to the user.

How microservices and APIs are used together

Microservices vs. APIs are not competing technologies. While they serve different purposes, the combination of microservices and APIs can be used to build sophisticated applications that are more resilient and scalable than traditional monolithic architectures. A microservice may expose an API that allows other microservices to trigger its functionality or retrieve data from it.

For example, let's say you have a microservice that stores data in a database. Another microservice might need to retrieve this data in order to display it on a web page. To enable these two services to communicate, you would define an API that specifies how the data should be structured and what methods should be used to access it. Once you have defined this API, any number of other microservices can use it to communicate with the data-storing service.

Microservices + APIs: Realizing the benefits of composability

Microservices and APIs provide the core technologies that enable modularity and reusability — key tenets of composability. 

When designing your applications, efficiency is a key consideration that you can address by identifying which services can be isolated as a microservice and accessed via an API. You should also identify third-party services that can provide key functionality to reduce the amount of code and infrastructure you have to develop and maintain.  

Composing applications from existing services has become a force multiplier for development teams who don't want to reinvent the wheel each time they need to expand their functionality or scale to meet demand. Development teams are increasingly leveraging third-party APIs for tasks such as payment processing, communication, and content curation and delivery. By treating these services as a component in a microservice-based architecture, you can improve scalability and reduce costs.

Building scalable apps with microservices, APIs, and Contentful

Developing scalable and reliable applications requires a number of technologies. Whether discussing microservices vs. APIs, or any other technology for building applications, your team should identify clear requirements. This should include your product specifications, user expectations for functionality, and future plans for building on these. 

One of the biggest resource drains in both the development process and the ongoing operation of modern mobile and web applications is content curation and delivery. Developers can be held back from building the bespoke, value-delivering aspects of their applications by having to implement content management interfaces, APIs, and delivery networks, while the ongoing cost of hosting these tools can impact the viability of large-scale applications. While implementing microservices for this task addresses scalability, it comes with increased infrastructure and maintenance costs.

Contentful provides a comprehensive platform for content management and hosting. Our user-friendly interface allows your creators to create and update content (including text, images, audio, and video) across all channels — from your newsletters, to your websites, billboards, and even AI assistants. You can access all of your content on our high-speed, infinitely scaling CDN using our REST and GraphQL APIs, allowing you to build anything, and deliver it anywhere.

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