Implementing a FIFO (First-In-First-Out) approach using a queue is ideal for ensuring messages are delivered in the order they were sent. In this approach, messages are added to the end of the queue and processed in the same order they were received, maintaining chronological order. A LIFO (Last-In-First-Out) approach would reverse the message order, which is not suitable for messaging applications. Priority-based approaches may prioritize certain messages over others, potentially disrupting the order of delivery. Circular buffers are more suited for fixed-size data storage, not for maintaining message order in a dynamic messaging system.

Method overloading in OOP refers to defining multiple methods in the same class with the same name but different parameters. Method overriding, on the other hand, involves replacing a method in a subclass with a new implementation. This distinction is crucial for polymorphism and code reuse.

The Iterative SDLC model involves revisiting and refining work in multiple cycles, allowing for feedback incorporation and continuous improvement. On the other hand, the Incremental SDLC model delivers functionality in increments, providing tangible value early and enabling progressive development.

Secure RESTful APIs employ various mechanisms to protect data and authenticate clients. SSL/TLS encryption ensures that data transmitted between clients and servers is encrypted, preventing unauthorized access and eavesdropping. OAuth 2.0 is a popular authorization framework that allows secure token-based authentication, enabling clients to access resources on behalf of users without exposing sensitive credentials. JWT (JSON Web Tokens) are used for securely transmitting information between parties as compact, URL-safe tokens, facilitating stateless authentication and authorization in RESTful architectures. IP whitelisting restricts access to API endpoints based on predefined IP addresses, enhancing security by allowing only trusted clients to interact with the API. Each of these mechanisms plays a vital role in safeguarding RESTful APIs against common security threats such as data breaches, unauthorized access, and man-in-the-middle attacks.

The design pattern used to ensure a class has only one instance and provides a global point of access to it is the Singleton pattern. This pattern restricts instantiation of a class to a single object and provides a way to access that instance globally. It is commonly used in scenarios such as database connections, logging mechanisms, and configuration settings where having multiple instances can lead to issues like resource wastage or inconsistent behavior.

In a doubly linked list, each node contains references to the next node and the previous node. This is because each node has two pointers, one pointing to the next node and one to the previous node.

Journaling in a file system involves recording changes to data in a journal before actually writing them to the main storage. This technique enhances reliability by preventing data loss in case of unexpected system crashes or power failures. When a system crashes, the journal can be used to replay transactions that were not yet committed to the main storage, ensuring data consistency and integrity. As a result, journaling helps maintain the reliability and consistency of file systems, making them more resilient to failures and ensuring data integrity.

The SELECT DISTINCT keyword is used in SQL to retrieve only unique values from a specified column in a table. When you use SELECT DISTINCT, the query results will eliminate duplicate values, presenting only distinct values in the result set. This is particularly useful when you want to analyze or display unique entries without redundancy. It's important to note that SELECT DISTINCT operates on a single column or a combination of columns, and it can be combined with other clauses like WHERE for more specific filtering. Understanding how to use SELECT DISTINCT helps in generating accurate and concise reports or data analysis results.

The correct option is Planning. The first phase in the SDLC is Planning, where project goals, scope, requirements, and resources are defined.

The Agile Manifesto emphasizes individuals and interactions over processes and tools, valuing working software over comprehensive documentation, customer collaboration over contract negotiation, and responding to change over following a plan. These principles guide Agile teams in prioritizing people and adaptability in software development.