Last updated
April 25, 2024

Microservices vs APIs: Differences and Definition

Emma Jagger

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Main Difference Between API and Microservice

Microservices and APIs represent two methods of designing software in modular forms. This technique focuses on crafting smaller, independent units of software that work together to execute sophisticated operations. This approach proves more efficient than creating a single, extensive codebase for all functionalities.

Microservices are defined by an architectural style that breaks down software into compact, autonomous, and specialized segments. Each microservice is dedicated to addressing a distinct issue or executing a particular function.

Conversely, an API acts as a set protocol for interaction between two software entities. It delineates the necessary data inputs a software component requires to fulfill a task and the anticipated result.

While microservices utilize APIs to facilitate communication among themselves, developers may also employ APIs from external sources to incorporate existing features into their applications.

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Key Differences: Microservices vs. APIs

  • Architecture vs. Interface: Microservices are an architectural style that structures an application as a collection of small, autonomous services. In contrast, APIs (Application Programming Interfaces) are specifications that allow different software components to communicate.
  • Scope of Functionality: Each microservice is designed to perform a specific, narrowly focused task or to solve a single problem, whereas APIs define the methods of interaction between software components, including the requests for data and the structure of the expected responses.
  • Independence: Microservices operate independently of each other, each running in its own environment and managing its own data. APIs do not contain business logic themselves; they are merely the conduit through which services and applications interact.
  • Usage in Integration: APIs are essential for microservices architecture as they are the primary means by which the services communicate with each other. APIs can also be used to integrate functionality from external systems into an application, regardless of whether it uses a microservices architecture.
  • Development and Maintenance: Microservices can be developed, deployed, and updated independently, which allows for greater agility and scalability in software development. APIs, while they can be versioned and evolved, require careful management to ensure compatibility and to avoid disrupting existing integrations.
  • Target Users: Microservices are primarily a concern for backend developers and architects who design and build complex applications. APIs can be used by both backend and frontend developers and are crucial for developers integrating various software systems and services.


What are Microservices?

In the old "monolithic" manner of software development, an application lived in one place, was sold in a box, and support was offered as required. In microservices, we break the component parts down into individual services- microservices- and spin them up as containers in the cloud. A container is an application with its runtime requirements included in the package, like a virtual machine. We then use an API gateway to orchestrate all of these services into a distributed system (service-oriented architecture, or SOA), and accept requests from the front-end client. This part requires rigorous engineering by devops to reduce round trips, decrease latency, and increase API security at public-facing endpoints. It will also require API testing to ensure all of our microservices are operating as a team with load balancing, continuous integration, and continuous delivery. Once we're done, we will have an application that lives across many clusters, with minimal creation of new code on our part. We've just used what already works, and made it work in harmony. It'd probably look like this.

What is an API?

An API, or Application Programming Interface, is a set of rules that define how computers and applications can communicate with each other. If you recall the old switchboards that operators used to field phone calls to their destinations, APIs are a little like that. A client makes an HTTP request to an API at an _endpoint_ which it has access to. The API validates the request and passes the request to the destination server or program. The server sends a response back, first through the API, which then transfers it back to the client.  The API provides security by decoupling the consuming application from the infrastructure providing the service. Once an API service and a client exchange authentication keys, they communicate through the API, meaning they don't have full access to each other, but enough information can be passed to get work done.  

How Do APIs Work?

A client can issue certain kinds of requests (or HTTP "verbs"), of which there are four main types:

  • GET - This request reads information from a record in the database.
  • PUT- This request changes a record's information in the database.  
  • POST - This request creates a new record in the database.  
  • DELETE - This request removes a record from the database.  

We will use IP Geolocation to GET a resource from their API.

Our GET request will retrieve information based on our IP address. We are telling the API with the request header we want all of the content, and it is returned as a JSON file, which is a lightweight text file popular in REST APIs.

In your terminal, enter `curl '{YOUR API KEY}'`. You should get output similar to below:

"StatusCode ":"200StatusDescription":"OKContent ":{ "ip_address":"", "city":"York", "city_geoname_id":4562407, "region":"Pennsylvania", "region_iso_code":"PA", "region_geoname_id":6254927, "postal_code":"17402", "country":"United States", "\"count..."

See the status code of `200`? You have completed your first GET request!

This is how information is exchanged in REST APIs.

Emma Jagger
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