Top 46 API Design Interview Questions And Answers

Question 1

What is API Design?

Accepted Answer

**API design** is the process of building an intermediary interface for a system to system connection to expose data to application users and developers.

The fundamental API design influences how well users can consume it and the general user experience. This development process does not allow a single approach. Instead, it combines a series of guidelines to meet initial expectations and continue to work consistently. Application programming interface designers closely follow industry best practices, design patterns, API design principles, and user needs to develop software that presents excellent functionality.

Question 2

What REST stands for?

Accepted Answer

*REST* stands for *REpresentational State Transfer*. REST is web standards based architecture and uses HTTP Protocol for data communication. It revolves around resource where every component is a resource and a resource is accessed by a common interface using HTTP standard methods. REST was first introduced by Roy Fielding in 2000.

In REST architecture, a REST Server simply provides access to resources and REST client accesses and presents the resources. Here each resource is identified by URIs/ global IDs. REST uses various representations to represent a resource like text, JSON and XML. Now a days JSON is the most popular format being used in web services.

Question 3

Mention whether you can use GET request instead of PUT to create a resource?

Accepted Answer

No, you are not supposed to use POST or GET.  GET operations should only have view rights

Question 4

Mention what are resources in a REST architecture?

Accepted Answer

Resources are identified by logical URLs; it is the key element of a RESTful design.  Unlike, SOAP web services in REST, you view the product data as a resource and this resource should contain all the required information.

Question 5

Mention some key characteristics of REST?

Accepted Answer

Some key characteristics of REST includes

* REST is stateless, therefore the SERVER has no state (or session data)
* With a well-applied REST API, the server could be restarted between two calls as every data is passed to the server
* Web service mostly uses POST method to make operations, whereas REST uses GET to access resources

Question 6

What is cached response?

Accepted Answer

*Caching* refers to storing server response in client itself so that a client needs not to make server request for same resource again and again. A server response should have information about how a caching is to be done so that a client caches response for a period of time or never caches the server response.

Question 7

What are different types of Web Services?

Accepted Answer

There are two types of web services:

* **SOAP Web Services**: Runs on SOAP protocol and uses XML technology for sending data.
* **Restful Web Services**: It’s an architectural style and runs on HTTP/HTTPS protocol almost all the time. REST is a stateless client-server architecture where web services are resources and can be identified by their URIs. Client applications can use HTTP GET/POST methods to invoke Restful web services.

Question 8

What are the advantages of Web Services?

Accepted Answer

Some of the advantages of web services are:

* **Interoperability**: Web services are accessible over network and runs on HTTP/SOAP protocol and uses XML/JSON to transport data, hence it can be developed in any programming language. Web service can be written in java programming and client can be PHP and vice versa.
* **Reusability**: One web service can be used by many client applications at the same time.
* **Loose Coupling**: Web services client code is totally independent with server code, so we have achieved loose coupling in our application.
* **Easy to deploy and integrate**, just like web applications.
* **Multiple service versions** can be running at same time.

Question 9

Define what is SOA

Accepted Answer

*A Service Oriented Architecture (SOA)* is basically defined as an architectural pattern consisting of services. Here application components provide services to the other components using communication protocol over the network. This communication involves data exchanging or some coordination activity between services.

Some of the key principles on which SOA is based are mentioned below

*   The service contract should be standardized containing all the description of the services.
*   There is loose coupling defining the less dependency between the web services and the client.
*   It should follow Service Abstraction rule, which says the service should not expose the way functionality has been executed to the client application.
*   Services should be reusable in order to work with various application types.
*   Services should be stateless having the feature of discoverability.
*   Services break big problems into little problems and allow diverse subscribers to use the services.

Question 10

What are advantages of REST web services?

Accepted Answer

Some of the advantages of REST web services are:

* Learning curve is easy since it works on HTTP protocol
* Supports multiple technologies for data transfer such as text, xml, json, image etc.
* No contract defined between server and client, so loosely coupled implementation.
* REST is a lightweight protocol
* REST methods can be tested easily over browser.

Top 46 API Design Interview Questions

What is API Design?

What REST stands for?

What is cached response?

Mention whether you can use GET request instead of PUT to create a resource?

What are different types of Web Services?

Mention some key characteristics of REST?

Mention what are resources in a REST architecture?

What are advantages of REST web services?

Define what is SOA

What are the advantages of Web Services?

What are the core components of a HTTP Request?

What is SOAP?

Mention what are the different application integration styles?

What are the disadvantages of statelessness in RESTful Webservices?

What is UDDI?

What are disadvantages of SOAP Web Services?

How would you choose between SOAP and REST web services?

What are the primary security issues of web service?

What are the core components of a HTTP response?

What is the purpose of HTTP Status Code?

What are disadvantages of REST web services?

What's the difference between REST & RESTful?

What are the best practices to design a resource representation?

WebSockets vs Rest API for real time data? Which to choose?

Mention what is the difference between PUT and POST?

What are the best practices to create a standard URI for a web service?

What is the use of Accept and Content-Type Headers in HTTP Request?

What is statelessness in RESTful Webservices?

What is Payload?

Mention what is the difference between RPC or document style web services? How you determine to which one to choose?

What are the best practices for caching?

What are different ways to test web services?

Explain element?

What are the advantages of statelessness in RESTful Webservices?

What do you mean by idempotent operation?

What is difference between SOA and Web Services?

Which type of Webservices methods are to be idempotent?

Which header of HTTP response provides control over caching?

Explain Cache-control header

Explain what is the API Gateway pattern

Explain the difference between WCF, Web API, WCF REST and Web Service?

What is difference between OData and REST web services?

Name some best practices for better RESTful API design

What are the best practices to be followed while designing a secure RESTful web service?

What is Open API Initiative?

Enlist some important constraints for RESTful web services