What Is a Webhook? How Webhooks Work in Software Systems

A server-to-server HTTP callback mechanism used by a WMS to push event-driven notifications (for example, order status changes or inventory updates) to eCommerce systems, reducing the need for polling and improving latency.

Webhook An automated HTTP message sent when a defined event occurs in a software system. Webhooks push a small payload (or sometimes an empty notification) from a source application to a receiving URL the moment a specific event happens, rather than requiring the receiver to ask for updates.

Webhooks are a simple, efficient pattern for real‑time event delivery between services. One application (the sender) registers a target URL with another application (the receiver) and then sends an HTTP POST to that URL when the configured event occurs. The receiver processes the incoming request, validates it, and reacts—updating state, triggering business logic, or forwarding the event to internal systems like a WMS, analytics pipeline, or notification service.

How Webhooks Work

At a technical level the flow is straightforward: an event occurs, the sender formats an HTTP request (usually POST) with headers and a body that describe the event, and it transmits that request to a preconfigured endpoint. The receiver acknowledges with an HTTP status code; 2xx indicates success while 4xx/5xx indicate client or server errors. Many implementations add retries, exponential backoff, and dead‑letter handling for failed deliveries.

Common Use Cases

• Order Updates: E‑commerce platforms notify fulfillment systems when orders are placed, canceled, or updated so warehouses can pick and pack immediately.
• Payment Notifications: Payment gateways send transaction success or failure events to accounting and order management systems.
• Inventory Sync: Warehouses send inventory changes to marketplaces and ERPs to keep stock levels consistent.
• CI/CD Triggers: Source control services notify build systems about new commits or pull request merges to kick off pipelines.

Why Webhooks Matter

Webhooks reduce latency and resource waste. Instead of periodic polling, which requires frequent API requests and delays between polls, webhooks provide near‑instant notifications. That lowers API call volume, reduces costs for both parties, and improves user experience by reducing the time between an external event and internal reaction—critical for time‑sensitive logistics and fulfillment operations.

How Implementations Vary

Different services implement webhooks differently: payload format (JSON vs form data), authentication (shared secrets, HMAC signatures, mutual TLS), retry policies (fixed vs exponential), rate limits, and webhook management UIs. Some platforms let you subscribe to granular events (e.g., order.shipped), while others offer only broad topics. Understand both the sender’s guarantees and the receiver’s expectations before relying on a webhook stream in production.

Reliability And Delivery Patterns

Robust webhook systems assume failures. Common patterns include retries with backoff, delivery TTL, idempotent handlers (so repeated deliveries don't create duplicate side effects), and dead‑letter queues for manual inspection. Monitoring delivery metrics (success rate, latency, queue depth) helps detect provider issues early and prevents downstream disruption in operations like order fulfillment.

Practical Example

Imagine a marketplace that notifies a 3PL when a new order is paid. The marketplace sends a webhook with order ID, item SKUs, quantities, fulfillment SLA, and destination. The 3PL’s endpoint verifies the signature, confirms inventory, creates a pick wave in the WMS, and responds 200 OK. If the 3PL is temporarily unavailable, the marketplace retries several times and logs failures to an admin dashboard for manual reconciliation.

Operational Tips For Adoption

• Label: Use Idempotency — Design webhook handlers to safely ignore duplicate deliveries using unique event IDs.
• Label: Validate Signatures — Verify HMAC or similar signatures to prevent spoofed events.
• Label: Monitor Deliveries — Track success rates, latencies, and retry counts to spot issues early.
• Label: Provide A Management UI — Allow subscribing/unsubscribing, viewing recent deliveries, and replaying events.

In short, the Webhook is a lightweight, event‑driven HTTP mechanism that delivers near‑real‑time notifications from one system to another. When designed with idempotency, verification, retries, and monitoring, webhooks are a low‑cost, high‑value tool for connecting the systems that run modern warehouses, order platforms, and logistics stacks.