Can you explain what CRUD operations are and provide an example of each? How do you implement Create, Read, Update, and Delete operations in a RESTful API? What is the difference between PUT and PATCH HTTP methods in the context of CRUD operations? What are the main differences between SQL and NoSQL databases, and when would you use each? How do you ensure the security of a backend application? Can you explain the role of middleware in a backend framework like Express.js? How do you manage environment variables in a backend application?
