Modern online services rely on third-party APIs for authentication, payments, communication, identity verification, fraud detection, observability, and fulfillment. These dependencies are outside the direct operational control of the application owner and may experience regional outages, throttling, latency spikes, quota exhaustion, or behavior changes that surface as user-visible failures. This paper presents configuration-driven dynamic API routing, an architecture for resilient third-party service integration based on pluggable factor lists, real-time telemetry, circuit breakers, bulkhead isolation, and a closed-loop decision engine. A factor list defines operation-specific hard gates and weighted scoring functions that evaluate candidate providers using live metrics, regional policy constraints, quota state, latency, cost, and incident signals. The router separates routing policy from application code, allowing operators to adapt vendor selection at runtime without redeploying applications. We formalize the factor-list model, describe a request-time routing algorithm, present the event pipeline that computes sliding-window provider health metrics, and analyze failover behavior under degraded-provider scenarios. We also describe an anonymized SMS verification case study in which manual vendor switching was replaced by automated routing driven by completion-rate telemetry.

翻译：现代在线服务依赖第三方API进行身份认证、支付、通信、身份验证、欺诈检测、可观测性及订单履行。这些依赖项不在应用所有者的直接运维控制范围内，可能遭遇区域中断、限流、延迟峰值、配额耗尽或行为变更，进而导致用户可见故障。本文提出一种配置驱动的动态API路由架构，该架构基于可插拔因子列表、实时遥测、断路器、舱壁隔离及闭环决策引擎，实现弹性的第三方服务集成。因子列表定义了操作相关的硬性门控与加权评分函数，通过实时指标、区域策略约束、配额状态、延迟、成本及事件信号评估候选服务商。该路由策略将路由逻辑与应用程序代码解耦，允许操作人员在运行时调整供应商选择策略而无需重新部署应用。我们形式化了因子列表模型，描述了请求时路由算法，设计了计算滑动窗口服务商健康指标的事件管道，并分析了服务商降级场景下的故障转移行为。此外，我们通过一个匿名的短信验证案例研究，展示了如何用基于完成率遥测的自动路由替代人工供应商切换。