The WHERE clause is used in SQL to filter records based on specified conditions. It allows for conditional retrieval of data from a table, helping in narrowing down the results to meet specific criteria. Other clauses like ORDER BY and GROUP BY are used for sorting and grouping results, respectively.

Managing concurrent database access

Secure payment processing in Node.js involves integrating a trusted payment gateway API that supports HTTPS for encrypted communication. Additionally, implementing data encryption using libraries like Node.js crypto ensures sensitive data like credit card details are securely handled. Adhering to PCI DSS standards is crucial for e-commerce platforms to protect customer data privacy.

The primary purpose of a firewall in network security is to filter incoming and outgoing traffic based on predetermined security rules. It acts as a barrier between trusted internal networks and untrusted external networks, helping to prevent unauthorized access and protect sensitive data. Firewalls can be hardware-based or software-based.

The correct option is Mediator. The Mediator pattern facilitates communication between objects by encapsulating the interaction logic in a mediator object. This promotes loose coupling and enhances maintainability.

An Intrusion Detection System (IDS) plays a crucial role in network security by monitoring network traffic for any suspicious or malicious activity. It doesn't prevent all cyberattacks but rather detects potential threats in real-time, providing alerts to administrators so they can take appropriate action to mitigate the risk. IDS helps in identifying unauthorized access attempts, anomalies in network traffic, and other security breaches, contributing significantly to overall network security posture.

React.js is primarily used for building user interfaces in web development. It allows developers to create interactive and dynamic UI components that update efficiently when data changes. React.js focuses on the frontend aspect of web development, handling the visual presentation and user interaction of web applications.

The "Content-Type" header in RESTful API requests specifies the format of the data being sent in the request body. For example, it can be "application/json" for JSON data or "application/xml" for XML data.

A router's primary purpose is to direct network traffic between different networks. It uses routing tables to determine the best path for data packets to reach their destination. This includes directing data between devices on the same network and between different networks, such as a local network and the internet. Routers also provide network address translation (NAT) to allow multiple devices on a network to share a single public IP address.

The INSERT command is used in SQL to add new records (rows) to a table. It allows you to specify the values for each column in the new row or provide values for a subset of columns if the table allows NULL values or has default values defined.