Which of the following AWS services does not use key-value pairs?

Route 53 stands out as the correct answer because it is primarily a scalable Domain Name System (DNS) web service designed to route end users to Internet applications. It functions by translating human-readable domain names into IP addresses, allowing users to access websites without needing to remember numerical addresses.

Unlike services such as DynamoDB, which inherently use key-value storage models for organizing data, Route 53 utilizes DNS records that are not structured as key-value pairs. For instance, a DNS record might link a domain to an IP address but does not store data in the same way that databases do.

In contrast, S3, DynamoDB, and Lambda all incorporate key-value concepts in their operations. S3 utilizes a key (the object name) and a value (the object data) structure for storing files. DynamoDB is explicitly a key-value and document database, while AWS Lambda is a computation service that operates with event-based triggers, often managing event data in key-value formats when interacting with services like S3 or DynamoDB.

Understanding these distinctions clarifies why Route 53 is the only service among the options that does not operate on the basis of key-value pair storage.