Web Services vs. Micro Services: A Pragmatic Explanation

I often see engineers and even executives get hung up on the “Microservices vs. Web services” terminology as if it were an either-or choice. It simply is not.

Since web services and microservices are not a replacement for each other, the best way to learn about the differences between the two is by understanding each one of them, their types, their benefits, and their challenges.

Webservice vs. Microservice: What each one of them is

What is a Web Service?

In a nutshell, a webservice is a unit of functionality exposed as a “service” over the “web”.

Simple enough, right? 🙂

In the case of web services, “over the web” typically means “HTTP” (secure HTTP, or HTTPS, to be precise).
A “Web Service” is how we expose data and functionality to other systems in a platform-agnostic way. “Other systems” is the key here. The intended audience for web services is always another “system, ” which could be another web service or a user interface application.

What is a Microservice?

Microservice is a relatively modern architectural style that structures an application or business capability as a collection of small (micro), independently deployable functional services.

Structuring an application as a collection of microservices allows for increased development velocity, operational agility, and scalability.
You can set up autonomous teams, each working on a set of microservices and making changes to them independently without affecting other parts of the larger solution.

Microservices architecture is an alternative to the monolithic application architectural style.

Web services can be packaged and deployed as a microservice OR they can be part of a monolith.

A microservice can be a web service, but it doesn’t have to. For example, it can be a micro user interface or an event-driven microservice.

Microservices vs. Web services
Simplistic Illustration of microservices architecture with a mix of web services and other type of microservices

Webservice vs. Microservice: Their Types

Different Types of Web Services

There are different types of web services based on the request-response model they support.
The two most popular ones are REST and SOAP.

REST and SOAP Web services can both be implemented as part of a larger monolith or as independent microservices.
Modern microservices architectures typically implement web services as REST web services due to the advantages of REST vs. SOAP.

Different Types of Microservices

You can classify microservices in a couple of different ways.

First, you can say there are different types of microservices based on the programming model they use.

The two most popular programming models for mircoservices are event-driven and request-driven.

Event-driven microservices are triggered by events and typically use an event streaming layer such as Kafka or messaging layer such as MQ.

Request-driven microservices are nothing but web-services that are invoked by making an HTTP request to them.

Another way to classify microservices is based on the nature of the capability they provide. You can have either UI microservices (often called micro front ends) OR middleware microservices (often when people say “microservices”, they are typically referring to middleware microservices)

Webservice vs Microservice: Their Benefits

Benefits of Web Services

The main benefit of web services is that web services enable interoperability driven by standards between systems.

Before the rise of web services, the only way to expose data and functionality from one system to another was through a custom integration solution. This meant building a solution from scratch whenever you wanted to connect two systems.

Web services drove a huge change by providing a standard way – XML over HTTP (SOAP) or JSON over HTTP (REST) – to expose data and functionality as services.
This lowered the cost and time of integration, allowing enterprises to adopt paradigms such as service oriented architecture (SOA) and allowing an ecosystem of developer and test tools to flourish.

Benefits of Microservices

Much has already been said about the benefits of microservices. However, the main advantage of microservices is that it allows enterprises to be more agile and innovative and improve their time to market.

Microservices vs. Web services: Difference in Getting Started

Planning for web services should first center around the web service interface.
What data or functionality should it expose to its callers and in what format (REST or SOAP. What does the contract look like).

Once the interface is agreed upon, developers can leverage appropriate standards and frameworks (e.g. Spring Boot or just plain JAX-WS / JAX-WS) to implement the web services. Deployment and monitoring strategies for a given web service will vary depending on whether the web service is deployed as microservice(s) or part of the monolith.

Microservices, on the other hand, is an enterprise architectural style, and as such is a complex undertaking requiring up front planning, architecture and buy-in from key stakeholders and sponsors.

Conclusion

So, what is the difference between web services and microservices? Here are the most important differences between the two –

1. Web services are a way to expose data and functionality as services. Microservices are an architectural style to improve feature velocity and business agility.

2. Web services can be (but don’t have to be) packaged & deployed as microservices and microservices can implement web services (but don’t have to)

3. Web services focus more on the standard (SOAP vs. REST) and format of the request-response exchange between the web service and its caller. Microservices focus more on effectively developing, deploying, and operating micro applications at scale as part of a larger solution or business capability.