The purpose of debugging in API development is to identify and fix issues or errors in the API code and functionality. Debugging helps ensure that the API works as intended, and it is a critical step in the development process to deliver a reliable and error-free API to users. Debugging does not aim to introduce errors, enhance security, or slow down the API.

API security concerns include protecting against unauthorized access, SQL injection, and data breaches. SQL injection is a type of attack where an attacker injects malicious SQL code into input fields, potentially compromising the database and exposing sensitive information.

Monitoring a critical API requires tracking relevant metrics. Prioritizing error rates and system resource utilization (Option 3) is the most appropriate choice, as it helps identify issues and performance problems. Response times are essential but should not be the sole focus. Option 1 suggests ignoring anomalies, which is not advisable, and option 2 is less relevant to anomaly response. Option 4 lacks the essential focus on error rates and resource utilization.

The correct approach to securely store and use an API key is to utilize environment variables or a secure key management system. Storing API keys in plain text or in version-controlled files is insecure and should be avoided. Encrypting and storing in a restricted database could be an option but may not be as secure as using dedicated key management solutions.

The primary purpose of API authentication is to ensure data privacy and security. It verifies the identity of the user or application requesting access to an API, preventing unauthorized access and protecting sensitive data. This security measure is vital in modern web development to safeguard user information and maintain the integrity of the API.

In this situation, OAuth 2.0 is employed to securely expose user data to third-party apps. OAuth acts as a resource server, authenticating and authorizing these apps, and issuing access tokens. It ensures controlled access to user data without exposing sensitive information directly. JWTs can also be used to include user data in the token if necessary.

The primary data format used in GraphQL APIs is JSON (JavaScript Object Notation). JSON is a lightweight and human-readable format, making it well-suited for data exchange between clients and GraphQL servers. GraphQL can also work with other data formats, but JSON is the most common.

To keep the user interface updated in a social media application using GraphQL, you should use GraphQL subscriptions. Subscriptions enable the server to push real-time updates to clients over WebSocket connections, providing efficient and responsive real-time communication.

OAuth 2.0 is primarily used for authentication and authorization in web applications. It allows a user to grant limited access to their resources on one site to another site without sharing their credentials. It is commonly used for user authentication and secure data access between different web applications.

Postman is a commonly used tool for automated API testing. It provides a user-friendly interface for creating, managing, and running API tests. With Postman, you can send requests, set up test suites, and automate API testing to ensure that your APIs function correctly and reliably.