Comprehensive and Detailed Explanation From Exact AWS AI documents:

Amazon Neptune is a fully managed graph database service optimized for storing and querying highly connected data.

AWS guidance highlights that graph databases are ideal for:

Fraud detection

Relationship analysis

Pattern discovery across entities such as users, transactions, and accounts

Amazon Neptune supports popular graph models and enables ML-driven investigations by efficiently traversing relationships, which is critical for fraud pattern analysis.

Why the other options are incorrect:

OpenSearch (A) is optimized for search and log analytics.

Aurora (B) is a relational database, not graph-based.

MemoryDB (D) is an in-memory data store for low-latency workloads.

AWS AI document references:

Amazon Neptune Overview

Graph-Based Fraud Detection on AWS

Using Graph Databases for Investigations