Payment systems face synchronization challenges when relying on polling to check transaction status. A real incident where a bank approved a payment but the backend marked it as failed due to delayed status updates illustrates the problem. Webhooks provide immediate, event-driven notifications when payment state changes, eliminating the lag and ghost states created by repeated polling. While webhooks require handling duplicates and out-of-order events, they deliver truth at the moment it happens rather than discovering it later through repeated checks.