The incident "Momo Payment Gateway Down" points to an API gateway or upstream service failure. Gateway timeouts (HTTP 502/503/504) in telecom fintech environments are typically caused by one or more backend services becoming unresponsive — due to high CPU load, memory exhaustion, database connection saturation, or a deployment that introduced a regression. In a Critical severity scenario, this likely affects a significant portion of end-user transactions. Connection pool limits being reached, misconfigured load balancer health checks, or a cascading failure from a dependent microservice are also common root causes.