GMD-AD: A Graph Metric Dimension-Based Hybrid Framework for Privacy-Preserving Anomaly Detection in Distributed Databases

Distributed databases are increasingly used in enterprise and cloud environments, but their distributed architecture introduces significant security challenges, including data leaks and insider threats. In the context of escalating cyber threats targeting large-scale distributed databases and cloud-native microservice architectures, this paper presents Graph Metric Dimension-based Anomaly Detection (GMD-AD), a novel graph-structure model designed to enhance cybersecurity in distributed databases by leveraging the metric dimension of interaction graphs; further, GMD-AD addresses the critical need for real-time, low-overhead, and privacy-aware anomaly detection mechanisms. The model introduces a compact resolving set as landmarks to detect intrusions through distance vector variations with minimal computational overhead. The proposed framework offers four major contributions, including sequential metric dimension updates to support dynamic topologies; a parallel BFS strategy to enable scalable processing; the incorporation of the k-metric anti-dimension to provide provable privacy against re-identification attacks; and a hybrid pipeline in which resolving-set subgraphs are processed by graph neural networks prior to final classification using gradient boosting. Experiments conducted on the SockShop microservices benchmark and a real MongoDB sharded cluster with injected anomalies reveal 60% reduced localization latency (1200 ms → 480 ms), stable detection accuracy (>0.997), increased noise robustness (F1 0.95 → 0.97) and a drop of re-identification success rate from the baseline by 40 percentage points (68% → 28%) when k = 3, ℓ = 2. We demonstrated up to 60% latency reduction and 40% privacy improvement over baselines, validated on real MongoDB clusters. The findings show that GMD-AD is a scalable, real-time and privacy-preserving HTTP anomaly detection solution for both distributed database systems and microservice architectures.