Mitigating Webhook Event Amplification in Multi-Tenant SaaS Integrations Using Delta-Validated Event Propagation

Abstract

Multi-tenant Software-as-a-Service (SaaS) platforms rely on webhook change notifications from cloud APIs such as Microsoft Graph to synchronize calendar and resource-booking data in near-real time. Empirical analysis reveals a structural failure in this model, which we term webhook event amplification: a single state mutation triggers a burst of unordered notifications carrying no deduplication token. Controlled measurement shows the provider delivering approximately nine times the notifications the subscription model warrants, reaching a mean of 53 notifications per mutation in the most severe configuration. Left unmitigated, this exhausts downstream compute, degrades observability, and introduces race conditions that compromise transactional idempotency. Because providers offer no native suppression and delta queries target periodic synchronization rather than real-time deduplication, remediation must occur at the subscriber edge. This paper introduces the Distributed Notification Broker (DNB), which interposes a four-stage filtering pipeline between the webhook source and downstream consumers, combining tenant-isolated partition-keyed streaming, delta-validated event propagation, and content-hash business-change detection so that only verified, business-relevant changes propagate. Empirical evaluation over a 78-day observation period demonstrates an 88% reduction in downstream processing volume, a substantial reduction in concurrency-induced race conditions restoring system stability, an 89% reduction in volume-attributable infrastructure cost, and a 68% reduction in total infrastructure cost.