The correct answer in this scenario is to use the OCI API Gateway service and configure rate limiting. Using the OCI API Gateway service and configuring rate limiting is an effective approach to address Distributed Denial-of-Service (DDoS) attacks. By implementing rate limiting, you can control the number of requests that can be made to your web service within a specific time frame. This helps to prevent overload and ensures that your service can handle legitimate traffic while mitigating the impact of DDoS attacks. By leveraging the OCI API Gateway service, you can easily configure rate limiting rules to restrict the number of requests per second or per minute. This allows you to set appropriate thresholds and safeguard your web service from being overwhelmed by excessive requests. The API Gateway acts as a protective layer, filtering out malicious traffic and ensuring the smooth operation of your service. While options like OCI Virtual Cloud Network (VCN) segregation and third-party service integrations may contribute to overall security, they do not specifically address DDoS attacks as efficiently as rate limiting. VCN segregation focuses more on network segmentation and isolation, while third-party service integration may introduce additional dependencies and complexities. Re-writing your web service and implementing rate limiting is a viable option, but it may not be feasible considering the time constraints mentioned. Leveraging the OCI API Gateway service provides a quicker and easier solution to implement DDoS attack mitigation through rate limiting.