APIs and microservices are central to web application and development and design, but while they’re both vital to these processes, they have differences in their function and how they’re applied. Here’s what you need to know about the differences between microservices and APIs.
What are microservices?
Microservices are an architectural style where a single application is built as a collection of small, independently deployable services, each responsible for one business capability. Each service has its own data store, its own deployment lifecycle, and its own team. Services communicate over the network, usually through APIs (often REST or gRPC), and the whole application is composed of many services calling each other. The point of microservices is independence: teams can ship changes to one service without coordinating across the rest of the application.
A microservice is a service-oriented architecture , an individual service in the microservice architecture. As its name suggests, a microservice divides different functions in an application into smaller components known as services.
Microservices can help transition away from monolithic systems as teams embrace a more modular and agile approach to software development.
For much more detail, see also “Microservice API patterns: a language for API design.”
The benefits of microservices include:
Time-saving updates: With microservices, making an update doesn’t require modifying the entire system. This allows you to perform rolling updates instead of time-consuming major updates. In addition, microservice updates can save money and debugging efforts.
A simpler experience: Because you’re working with microservices, you don’t have to understand the system architecture to understand a single aspect of the software.
Failure doesn’t knock down the entire application: Unlike with APIs, if a microservice fails it doesn’t affect the entire application. Similarly, if the security of a microservice is compromised, it doesn’t affect the entire application.
What are APIs?
APIs (application programming interfaces) are contracts that let one piece of software call another. An API defines what requests you can make, what data shapes go in and out, what errors can come back, and what authentication is required. APIs are how microservices talk to each other, how mobile apps talk to backends, how partners integrate with platforms, and how AI agents call out to tools. Where microservices are an architectural pattern, APIs are the interface contract that makes any cross-service communication possible.
An API , short for application programming interface , is part of an application that communicates with other applications. APIs are used to build a variety of applications, tools and more.
Dive deeper into an API definition and how they work here.
The benefits of APIs include:
Simple functionality and flexibility between systems: When a customer orders something, they can track the shipment of their goods via a phone or other mobile device.
Greater productivity: APIs let you quickly implement existing functionality instead of adding new things from scratch. You can integrate various analytics tasks so that you can realize your business goals faster.
More cost savings: Building an app can add up financially, but APIs can significantly reduce your development efforts and costs.
Microservices and API FAQs
What is the difference between microservices vs API and between API and microservices? Microservices vs API: microservices are an architectural style for decomposing one application into many independently deployable services; APIs are the contracts those services use to talk to each other and to the outside world. The difference between API and microservices is that APIs are interfaces (what), microservices are services (how the application is built).
What is the difference between microservices vs web services and web services vs microservices? Microservices vs web services and web services vs microservices: web services (SOAP, classic XML-RPC) are an older interface style that exposes operations over HTTP, often coupled to a monolithic backend. Microservices are an architectural style that may expose REST, gRPC, or event-driven APIs. The differences between microservices and web services boil down to scope (microservices = small service + own data; web service = interface only), protocol (microservices favor REST and gRPC; web services lean SOAP), and deployment (microservices are independently deployable, web services usually are not).
How do microservices APIs relate to one another? Microservices APIs are the contracts that microservices expose. Each microservice owns at least one API. Inside the application, microservices talk to each other through APIs (internal service-to-service). Outside, the public product API is built by composing or routing to those internal APIs. API in microservices is therefore both the internal connective tissue and the external product surface.
Is an API a microservice? Is an API a microservice? No. An API is a contract that defines how software is called; a microservice is a small, independently deployable service that may expose one or more APIs. A microservice usually has an API; an API does not have to belong to a microservice (monoliths and SaaS platforms also expose APIs).
What is API microservices architecture and API and microservices architecture? API microservices architecture (or API and microservices architecture) is the production pattern where the application is built as microservices internally, the external surface is an API gateway that routes to those microservices, and a federated API management platform governs both the internal and external APIs.
What is web API vs microservices and web service vs API vs microservices? Web API vs microservices: a web API is an interface (often REST over HTTPS); microservices is an architectural style that may expose web APIs. Web service vs API vs microservices: a web service is an older interface style (SOAP), an API is the broader interface concept (REST, GraphQL, gRPC, event-driven), and microservices is the architectural decomposition pattern. They are not alternatives; they are layers.
Differences between APIs and microservices
How microservices and APIs work together
In a real production system, microservices and APIs work together at three layers.
- Internal service-to-service APIs. Each microservice exposes APIs (REST, gRPC, or event-driven) to other microservices in the same application. These APIs are usually private, fast, and optimized for engineering teams.
- External product APIs. A subset of capability is exposed to external developers, partners, or mobile and web clients. These APIs are versioned, documented, secured, and often monetized. They sit behind an API gateway that handles authentication, rate limiting, and observability.
- Federated governance. Across many microservices and many external APIs, a federated API management platform (such as Amplify Fusion) gives you one inventory, one policy plane, and one observability story without forcing every team onto the same gateway.
The TL;DR: microservices are how you build, APIs are how you expose, and an API management platform is how you keep both under control as the number of services and consumers grows.
Microservices vs APIs side by side
Compare the two concepts across five dimensions to see where the line sits.
| Dimension | Microservices | APIs |
|---|---|---|
| What it is | Architectural pattern for building an application | Contract for software-to-software communication |
| Scope | How an application is decomposed | How any two pieces of software interact |
| Unit | A service with its own deployment, data, and team | A set of endpoints and request/response shapes |
| Lifecycle | Built, deployed, and operated as a unit | Designed, versioned, governed, and monetized as a contract |
| Relationship | Microservices use APIs to talk to each other | APIs can be exposed by microservices, monoliths, or SaaS platforms |
Microservices and APIs are related but not the same. Microservices are the architectural style (how you decompose an application). APIs are the contract (how services talk to each other). Every microservices architecture is built on APIs, but not every API belongs to a microservice. A monolithic application can expose APIs to its consumers. A SaaS platform exposes APIs to partners regardless of its internal architecture. Microservices is a how-you-build decision; APIs is a how-you-expose decision. Most production systems combine both: microservices internally, APIs externally and between services.
APIs and microservices are different things, but they are often used together. APIs and microservices serve different purposes; APIs are interfaces for communication, while microservices are architectural components.
A few differences between the two include:
- Size. Microservices are small, while APIs are larger, especially in complex integration cases.
- Microservices are quicker to build than APIs.
- Microservices are components, while APIs are an interface.
An API serves as a contract for interactions within the microservices, allowing interaction between the two.
We hope this answers a few of your questions on APIs and microservices.
To get a better understanding of how they work in the real world, read about how moving from a monolithic IT architecture to reusable, API-enabled microservices helped one construction equipment manufacturer accelerate development, enhance security, and reduce costs.
Learn 6 ways an open API management platform makes life easier for IT leaders.