Top FastAPI Interview Questions and Answers (2026)

FastAPI Interview Questions for Freshers

FastAPI is a modern web framework for building APIs with Python, thus helping build applications faster and more efficiently. It was created by Sebastian Ramirez and released in 2018 as an open-source framework. FastAPI boasts a high level of performance comparable to Go and Node.js, which is achieved through Python’s type hints and asynchronous programming.  

Many companies worldwide use FastAPI to develop robust and scalable web applications and APIs. In this article, check out FastAPI interview questions and answers that can help you confidently prepare for your next job interview.

1. What is FastAPI?

• FastAPI is a Python web framework for building modern rest APIs
• Fast API keeps everything simple. But scalable and Extensible for the developer
• Fast API handles all the business logic for the application

2. How is FastAPI different from other frameworks?

FastAPI differs from other Frameworks due to its built-in API documentation, highly permanent nature, automatic generation of open API, support for asynchronous programming and JSON schema documentation.

3. What are the benefits of using FastAPI?

The benefits of FastAPI Include 

•   Built-in API documentation
•   Simple deployment to cloud nature
•   Highly permanent nature
•   Automatic generation of open API
•   Support for asynchronous programming
•   Easy Integration with Other Python Libraries
•   JSON schema documentation

4. What are the features of FastAPI?

• Fast and Fast to code
• Few Bugs
• Quick and Eazy to use, FAST API is developed in the developer's mind
• Robust
• Fast API uses the open standards and JSON Schema
• It takes less time to read the docs.

5. What are the Top companies using FastAPI?

• Netflix
• Google
• Microsoft

6. What are the different types of request parameters supported in FastAPI?

FastAPI supports 3 types of request parameters:

1. Query Parameters
2. Path Parameters
3. Request Body Parameters

7. How do you define a route in FastAPI?

To define a route in FastAPI, use the following syntax @app.route() decorator followed by the HTTP method.

Example:

            
    @app.get('/student/{student_id}')
            

    defines GET route with a parameter student_id

8. What is Dependency Injection in FastAPI?

Dependency injection in FastAPI is a design pattern in which the system does whatever is needed to provide your code with needed dependencies. It will easily inject the dependencies into other components that require them.

This is useful in the following cases

• share database connections
• with the same code logic again and again (or shared logic)
• Role Requirements, Enforce security, Authentication.
• and Many more

9. How do you define a dependency in FastAPI?

Use the 'Depends' function decorator to define a dependency in FastAPI

You can import it directly from fast API:

            from fastapi import Depends;

10. Why is logging important in FastAPI applications?

Logging is very important in FastAPI applications to understand its behaviour, monitor its performance, and diagnose issues. It provides a way to record information, errors, warnings, and other related details during runtime. 

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