Option A refers to PolarDB Global Database Network (GDN), Alibaba Cloud ' s architecture for connecting PolarDB clusters across regions. A GDN contains a primary cluster and secondary regional clusters. Data changes are continuously replicated, local reads can be served by regional clusters, and write operations are routed to the primary cluster. Maintaining a single authoritative write path is particularly important for reservation transactions where concurrent booking operations must be controlled consistently.

Option C provides resilient application capacity by deploying ECS application servers in multiple regions and using ALB within each regional deployment to distribute requests among healthy instances. In a complete production implementation, a global routing mechanism such as DNS traffic management or Global Accelerator would normally direct users between those regional application stacks.

Function Compute is suitable for payment-gateway integrations because payment callbacks and API interactions are event-driven or request-driven workloads. Function Compute can be exposed securely through API Gateway, which provides routing, authentication, traffic control, and API management without persistent integration servers.

OSS versioning is useful for protecting stored objects but does not supply the transactional database, regional application availability, or payment-processing functionality required here.

Study Guide reference: Building Highly Available, Performant Cloud Architecture — multi-region PolarDB, GDN, regional application tiers, ALB, and serverless integration.

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The threats described exist at different layers, so the architecture should apply layered protection. WAF is the correct control for public HTTP/API traffic because it analyzes application-layer requests and blocks threats such as SQL injection, cross-site scripting, command injection, brute-force attacks, and other OWASP-style attacks. Alibaba Cloud explicitly supports integrating WAF with API Gateway and recommends disabling direct access paths afterward so clients cannot bypass WAF.

Large DDoS attacks require a dedicated volumetric mitigation service. Anti-DDoS Proxy scrubs malicious network and transport-layer traffic before clean traffic is forwarded toward the application infrastructure. Alibaba Cloud ' s Anti-DDoS architecture supports protected services behind Server Load Balancer resources and provides port-forwarding mechanisms for non-HTTP workloads.

Alibaba Cloud specifically recommends combining Anti-DDoS and WAF when an application needs protection against both large volumetric attacks and sophisticated application-layer exploits.

WAF should protect the HTTP/API application boundary rather than being treated as a general Layer-4 NLB firewall. Security Center provides workload security and posture management, while basic DDoS protection alone is less suitable for the question ' s explicitly stated large and sophisticated attacks.

Study Guide reference: Securing Workloads on Alibaba Cloud — WAF, Anti-DDoS, API Gateway security, and defense-in-depth.

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ROS Stack Groups are specifically designed for centrally deploying a common Resource Orchestration Service template across multiple Alibaba Cloud accounts and regions. This makes option D the architecture that directly addresses both dimensions of the requirement: multi-account governance and multi-region infrastructure-as-code deployment.

Alibaba Cloud documentation states that stack instances belonging to a stack group can deploy stacks into destination accounts and different regions. With Resource Directory integration and service-managed permissions, trusted access can be enabled so that stack groups are operated by a management account or delegated administrator while deployments occur in organization member accounts.

Nested stacks are primarily a template-composition mechanism; they do not constitute centralized multi-account deployment orchestration. Manually combining ordinary ROS templates and RAM policies could technically enable cross-account operations, but it recreates functionality that Stack Groups provide natively and increases operational overhead. Resource Directory and Cloud Governance alone also do not replace the actual multi-account, multi-region stack deployment mechanism.

Therefore, Resource Directory establishes the organizational account structure while ROS Stack Groups provide repeatable infrastructure deployment across those accounts and target regions.

Study Guide reference: Core Infrastructure Deep Dive; Resource Orchestration Service, multi-account governance, and repeatable cloud architecture.

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