20 OpenAPI Interview Questions and Answers

OpenAPI is a specification used for describing and documenting REST APIs. It is language agnostic and can be used with any programming language. Understanding OpenAPI and being able to answer questions about it during an interview can help you land a position in the field of API development. In this article, we will review some common OpenAPI questions and how you should answer them.

OpenAPI Interview Questions and Answers

Here are 20 commonly asked OpenAPI interview questions and answers to prepare you for your interview:

1. What is OpenAPI?

OpenAPI is a specification for describing REST APIs. The specification defines a set of rules and guidelines that developers can use to create APIs that are easy to use and consistent.

2. Why was OpenAPI developed and what are some of its advantages over other API management solutions?

OpenAPI was developed as a way to standardize the way that APIs are described and documented. This has a number of advantages, including making it easier for developers to understand how an API works, and making it easier to automate the process of creating and maintaining API documentation. OpenAPI is also designed to be easily extended, so that it can be customized to fit the needs of any particular project.

3. How do you define the basic information about your API using OpenAPI?

The basic information about your API is defined using the “info” object. This object contains information about the title, version, and description of your API.

4. Can you explain which HTTP methods (verbs) can be used with an endpoint in OpenAPI?

The HTTP methods that can be used with an endpoint in OpenAPI are GET, POST, PUT, PATCH, and DELETE.

5. What’s the difference between a request body and a response body in context with OpenAPI?

A request body is the body of the HTTP request that is sent to the server when making an API call. This request body can contain various information, such as the data that you are trying to submit to the API. A response body is the body of the HTTP response that is received from the server after making an API call. This response body can contain various information, such as the data that you have requested from the API.

6. What do you understand by “HTTP status codes” as mentioned in OpenAPI specifications?

HTTP status codes are a set of standard codes that are used to communicate the status of a request. For example, a “200” code indicates that a request was successful, while a “404” code indicates that a requested resource could not be found.

7. Can you use OpenAPI to specify that only certain query parameters should be passed with a request? If yes, how?

Yes, you can use the required field in the parameters object to specify that a parameter is required.

8. How do you specify the type of request body expected by an endpoint in OpenAPI?

You can specify the type of request body expected by an endpoint in OpenAPI using the “in” field. This field takes a string value that can either be “query”, “header”, “path”, or “cookie”.

9. Is it possible to describe multiple responses for an endpoint in OpenAPI? If yes, then how?

Yes, it is possible to describe multiple responses for an endpoint in OpenAPI. This can be done by using the “responses” keyword, followed by a list of different response codes that the endpoint could return. For each response code, you would then provide a description of the corresponding response.

10. What do you understand by media types in OpenAPI?

Media types are a way of specifying the format of a message body when sending or receiving data. In OpenAPI, media types are used in the request and response bodies of an operation. For example, if you are sending data in JSON format, you would specify a media type of application/json.

11. How do you describe different error scenarios when used with an endpoint in OpenAPI?

When you are describing an endpoint that can return errors, you will need to include a section in your OpenAPI definition that outlines the different error scenarios that could occur. This will help developers understand what could go wrong when they are using your API, and how to handle those errors.

12. Is it possible to use JSON schema extensions when specifying endpoints in OpenAPI? If yes, then how?

Yes, it is possible to use JSON schema extensions when specifying endpoints in OpenAPI. You can do this by adding a “x-” prefix to the name of the extension, followed by the name of the extension. For example, if you wanted to use the “foo” extension, you would add “x-foo” to the name of the endpoint.

13. What happens if there is a validation error while processing a request in OpenAPI?

If there is a validation error while processing a request in OpenAPI, then the request will be rejected and an error message will be returned.

14. How do you describe security requirements for an endpoint in OpenAPI?

You can describe security requirements for an endpoint in OpenAPI by using the securityDefinitions and security sections. In the securityDefinitions section, you can define the type of security that will be used for the endpoint. In the security section, you can specify which security requirements apply to the endpoint.

15. What are the best practices you should follow while defining endpoints using OpenAPI?

While there are many different ways to structure an OpenAPI document, it is generally recommended that you group your endpoints by resource. So, for example, if you have an API for a blog, you might have a resource for posts, and each endpoint for posts would be grouped together. This makes it easier for consumers of your API to understand what each endpoint does, and also makes it easier to maintain your API over time.

16. How do you model a one-to-many relationship using OpenAPI?

You can use the $ref keyword to reference a schema that defines the relationship.

17. What are some ways to avoid duplication while using OpenAPI?

One way to avoid duplication while using OpenAPI is to use the $ref keyword. This keyword allows you to reference already defined objects, making it easy to reuse components without duplicating code. Another way to avoid duplication is to use the allOf keyword. This keyword allows you to combine multiple schemas into one, which can help reduce duplication if you have similar objects.

18. What tools can you use to automatically generate documentation from OpenAPI specs?

There are a few different tools that can be used to automatically generate documentation from OpenAPI specs. One popular tool is Swagger, which can be used to generate both HTML and JSON documentation. Another tool that can be used is ReDoc, which focuses on generating HTML documentation.

19. Can you give me examples of real-world uses of OpenAPI?

OpenAPI is often used in the development of web-based applications. It can be used to create APIs that allow different applications to communicate with each other. It can also be used to create documentation for APIs.

20. What version of OpenAPI are you most familiar with?

I am most familiar with OpenAPI 3.0.