# REST, SOAP, AsyncAPI and GraphQL API styles

*MuleSoft Integration Foundations Study Guide · Recognize and interpret essential integration concepts and terminology · Last updated November 2, 2026 · https://www.certifyforce.com/study-guide/mulesoft-integration-foundations/essential-integration-concepts-and-terminology/rest-soap-asyncapi-and-graphql-api-styles*

How to classify an API from its clues: REST resources and HTTP methods, SOAP's WSDL and XML envelope, GraphQL's single endpoint with client-chosen fields, and event-driven APIs described with AsyncAPI events, channels and transports, plus when asynchronous beats synchronous.

- Certification: Salesforce MuleSoft Integration Foundations
- Exam section: Recognize and interpret essential integration concepts and terminology
- Study guide: https://www.certifyforce.com/study-guide/mulesoft-integration-foundations

**Official exam objective:**

> Identify and classify RESTful, SOAP, AsyncAPI, and GraphQL APIs.

## What the exam expects

- Classify an API as REST, SOAP, GraphQL or event-driven (AsyncAPI) from clues such as WSDL, a single query endpoint or subscribers.
- Place SOAP and GraphQL in MuleSoft's RPC family and explain how that differs from REST.
- Describe AsyncAPI's three layers (events, channels, transport) and where AsyncAPI specs are authored.
- Choose between a synchronous and an asynchronous API for a requirement.

Key terms:
- **SOAP web service**: a web service that exchanges XML envelopes under strict protocols, described by a WSDL.
- **WSDL**: the definition that describes a SOAP backend's operations.
- **GraphQL**: a query language for APIs that offers one endpoint across data sources and returns only requested fields.
- **Event-driven API**: an API whose response is triggered by an event rather than a consumer's call.
- **AsyncAPI**: an open, technology-agnostic language that describes messaging interfaces.

## Key facts

| Fact | Detail | Source |
|---|---|---|
| RPC-style technologies | SOAP, GraphQL and gRPC | [Types of APIs](https://www.mulesoft.com/api/types-of-apis) |
| RPC drawback | Protocol-agnostic, so it loses native features such as caching | [Types of APIs](https://www.mulesoft.com/api/types-of-apis) |
| SOAP proxy requirement | A WSDL definition of the backend service | [SOAP proxies](https://docs.mulesoft.com/api-manager/latest/building-soap-proxy) |
| SOAP validator always checks | Valid SOAP action and valid SOAP envelope | [SOAP proxies](https://docs.mulesoft.com/api-manager/latest/building-soap-proxy) |
| SOAP transports | HTTP, and also JMS, FTP or SMTP | [Examine APIs](https://trailhead.salesforce.com/content/learn/modules/application-networks-and-api-led-connectivity-in-mulesoft/examine-apis-and-web-services) |
| GraphQL origin | Facebook, open-sourced 2015, GraphQL Foundation | [What is GraphQL](https://www.mulesoft.com/api/what-is-graphql) |
| AsyncAPI layers | Events, channels, transport | [AsyncAPI specs](https://docs.mulesoft.com/design-center/design-async-api) |
| Async result delivery | Polling, webhook or WebSockets | [Async APIs](https://www.mulesoft.com/api/what-is-asynchronous-api) |

## Check yourself

- Why does MuleSoft say RPC-style APIs tighten coupling between consumers and providers?
- When the SOAP action in an inbound request is empty, how does the SOAP proxy find the operation?
- Why does GraphQL make versioning simpler than `/v1/`-style endpoints?
- How do you start a new AsyncAPI specification in Design Center?

## Sources

- [Types of APIs and how to determine which to build](https://www.mulesoft.com/api/types-of-apis)
- [What is GraphQL? An introduction](https://www.mulesoft.com/api/what-is-graphql)
- [What are asynchronous APIs?](https://www.mulesoft.com/api/what-is-asynchronous-api)
- [AsyncAPI Specifications](https://docs.mulesoft.com/design-center/design-async-api)
- [Build SOAP API Proxies](https://docs.mulesoft.com/api-manager/latest/building-soap-proxy)
- [Examine APIs and Web Services (Trailhead)](https://trailhead.salesforce.com/content/learn/modules/application-networks-and-api-led-connectivity-in-mulesoft/examine-apis-and-web-services)
- [What is REST API design?](https://www.mulesoft.com/resources/api/what-is-rest-api-design)

## About the full unit

The "Core concepts", "Exam traps" and "Worked scenario" sections of this unit, its 4 linked practice questions, and unlimited timed mock exams are included with the MuleSoft Integration Foundations pack (USD $19): https://www.certifyforce.com/practice-exams