What technology is primarily used to secure communication between a client's frontend and backend?

The primary technology used to secure communication between a client's frontend and backend is Transport Layer Security (TLS). TLS is a cryptographic protocol designed to provide secure communication over a computer network. It ensures that any data transmitted between the client and server is encrypted, which protects it against eavesdropping, tampering, and forgery.

In practice, TLS is an improvement over its predecessor, SSL (Secure Sockets Layer), which is still referenced but is considered outdated and less secure. While SSL and TLS are often discussed together, it is TLS that is actively used in modern secure communications. The adoption of TLS is important for building trust, particularly in web applications where sensitive information, such as payment details, needs to be safely transmitted.

HTTPS, which stands for Hypertext Transfer Protocol Secure, relies on TLS to secure HTTP communications. Thus, while HTTPS is indeed a secure protocol used for web traffic, it fundamentally utilizes TLS for the security aspect.

Firewalls, while essential for network security, do not inherently encrypt communications and are instead used to control incoming and outgoing network traffic based on predetermined security rules. Therefore, TLS is the most accurate answer when specifically regarding the technology that secures the communication itself.