Definition
A NAT gateway is a managed cloud service that enables instances in a private subnet to connect to the internet or other AWS services, but prevents the internet from initiating a connection with those instances. It acts as a traffic director, translating private IP addresses to a public IP address when outbound requests are made. This service is crucial for maintaining security by keeping internal resources inaccessible from the public internet while allowing them necessary outbound access. For instance, a web server in a private subnet can receive updates or send logs without being directly exposed to external threats. Unlike a NAT instance, which is a virtual machine you manage, a NAT gateway is a fully managed service offering higher availability and scalability. You will encounter NAT gateways on AWS certification exams like the Solutions Architect Associate and in cloud security certifications.