How Webhooks Work and When to Use Them Instead of Polling APIs

Every integration you build answers one question before it answers anything else: how does data move from the source system to the destination? The answer determines latency, resource cost, failure modes, and long-term maintenance burden. Two architectural patterns dominate this decision: polling, where your system asks for data on a schedule, and webhooks, where the source system sends data to you the moment something happens.

Neither is universally correct. Both are widely misapplied. And in enterprise platforms like Workday and Infor, the decision carries an added layer of complexity because the platforms themselves handle event delivery differently from the majority of modern SaaS APIs. This article explains both patterns at a technical level, establishes the criteria for choosing between them, and addresses the specific architectural realities that Workday and Infor users need to understand before making integration design decisions.

What Polling Actually Does Technically

Polling is a pull-based integration pattern. Your integration client sends a scheduled HTTP request to an API endpoint, receives a response payload, processes whatever changed since the last request, and waits for the next scheduled interval to repeat. The mechanics are straightforward, but the implementation details matter significantly.

A naive polling implementation requests the full dataset on every call. A production-grade polling implementation uses cursor-based or timestamp-based change detection, where each request includes a filter parameter that scopes the response to records modified after the last known checkpoint. In a Workday REST API context, this might look like a request to the Workers API that includes an updatedFrom parameter set to the timestamp of the previous successful poll. The API returns only workers whose records changed during that window, reducing payload size and processing overhead compared to a full dataset extract.

The critical variable in any polling architecture is interval design. This is where most integrations make their first technical mistake. A polling interval that is too long introduces data staleness, which in payroll or benefits contexts can produce downstream compliance failures. A polling interval that is too short burns through the API provider’s rate limit budget, triggers throttling, and can cascade into integration failures during peak business hours when the source system is under higher load. Workday’s REST API rate limits are tenant-specific and vary based on subscription tier and API domain, which means an interval that works cleanly in one environment may cause 429 Too Many Requests errors in another.

Polling also has a structural inefficiency that compounds at scale. Every API call executes regardless of whether there is new data to process. An integration polling the Absence Management API every 15 minutes will fire 96 times per day. If leave balances change on 2 of those calls and return empty sets on the other 94, the integration has performed 98 percent of its work to produce zero value. That overhead is benign at small scale and significant at enterprise scale across dozens of integrations running in parallel against the same tenant.

What Webhooks Actually Do Technically

A webhook is an event-driven HTTP callback. When a defined event occurs in the source system, the source system constructs a JSON or XML payload describing the event and sends an HTTP POST request to a URL endpoint that you have registered in advance. Your endpoint receives the payload, acknowledges receipt, and processes the event.

The full webhook delivery sequence involves five distinct steps that are worth understanding precisely:

Registration is the first step. You provide the source system with a callback URL and specify which event types you want to receive. The source system stores this subscription and monitors for matching events.

Triggering occurs when the registered event fires. The source system generates an event payload containing the event type, a unique event identifier, a timestamp, and the data describing what changed. This payload is typically JSON-structured.

Delivery is the HTTP POST from the source system to your endpoint. Most production webhook providers include a cryptographic signature in the request headers, generated using HMAC-SHA256 applied to the payload body with a shared secret. Your endpoint must verify this signature before processing the payload to prevent spoofed or tampered deliveries from being acted upon.

Acknowledgment is your endpoint’s 200 OK response. It must be sent quickly, before any processing logic runs. Most webhook providers enforce a tight timeout window on acknowledgment, after which the delivery is considered failed and retry logic kicks in. GitHub, for example, documents a 10-second acknowledgment window. Processing the event synchronously inside the request handler violates this constraint for any non-trivial workload.

Asynchronous processing follows acknowledgment. After returning the 200 OK, your handler writes the raw event payload to a durable queue and returns immediately. Worker processes consuming the queue handle the actual business logic, including data transformation, downstream API calls, database writes, and error handling. This separation is not optional in production systems. It is the architectural choice that determines whether your webhook integration is reliable or fragile.

The Operational Realities of Webhook Delivery

Webhooks are not guaranteed delivery systems by default. HTTP POST requests fail for reasons ranging from network timeouts to endpoint unavailability to TLS handshake errors. Production webhook architectures account for this with three mechanisms: retry logic, dead letter queues, and reconciliation jobs.

Retry logic at the provider level means that when a delivery fails or times out, the source system retries the delivery according to a defined schedule. Most providers implement exponential backoff with jitter to avoid thundering herd problems where a provider recovers from an outage and simultaneously retries thousands of queued deliveries. A typical retry schedule might progress through delays of 5 seconds, 25 seconds, 125 seconds, and 625 seconds before exhausting retry attempts.

Idempotency is a non-negotiable requirement for any webhook consumer that operates behind a retry mechanism. Because the same event may be delivered more than once, your processing logic must produce the same outcome regardless of how many times it runs for a given event ID. The standard implementation uses the unique event identifier included in every webhook payload: before processing, check whether you have already handled an event with this ID; if so, acknowledge receipt and discard without reprocessing.

Dead letter queues receive events that have exhausted all retry attempts. Without a dead letter queue, events that fail final delivery are silently dropped. With one, they are captured with full payload and metadata for investigation, manual resubmission, or automated replay after the underlying failure condition is resolved.

Reconciliation jobs run on a schedule, typically nightly, and compare the event log against the source system’s current state using an API query. This catches any gaps that survived the retry and dead letter queue mechanisms, which is important because no webhook delivery architecture eliminates the possibility of a missed event. Reconciliation is the backstop.

How Workday Handles This: The Critical Enterprise Nuance

Here is the point that most general-purpose articles on webhooks omit, and it directly affects every Workday integration architect reading this. Workday does not natively support outbound webhooks in the traditional sense. There is no mechanism to register a callback URL and receive an HTTP POST from Workday when an employee record is hired, transferred, or terminated. Workday’s role in event delivery is limited to serving the API responses that your integration polls against.

This is not a limitation of the REST API specifically. It reflects Workday’s integration architecture, which routes event-driven notifications through its own internal mechanisms rather than through standard HTTP callbacks.

Real-time event delivery in Workday integrations is built on three patterns, each with different tradeoffs.

The first is polling REST endpoints or Reports-as-a-Service (RaaS) on a schedule, using delta timestamps or cursors to retrieve only changed records. This is the most common pattern and the one most EIB and scheduled Studio integrations use. Its latency floor is defined by the polling interval, which means it is inherently not real-time. Understanding where polling breaks down in Workday-specific scenarios, and how to design around those breakdowns, is foundational to building reliable integrations. The most frequently encountered failure patterns in EIB-based integrations arise directly from polling architectures that were not designed to handle the edge cases produced by Workday’s object model and release cycle.

The second pattern is Workday Outbound Message Services. When a business process event occurs in Workday, such as the completion of a hire business process or the approval of a job change action, Workday can push an outbound message to a subscribing external system via a configured integration endpoint. This is the closest Workday gets to native webhook behavior. The subscribing system receives a notification that the event occurred and can then query Workday to retrieve the full data. This pattern is event-triggered but data-sparse on delivery: the notification payload describes that something happened but does not include the complete record, so the receiving system must issue a follow-up API call to get full context.

The third pattern is Workday Orchestrate’s event-driven integration model. According to Workday’s Integration Cloud documentation, Orchestrate supports event-driven integrations that instantly trigger predefined sequences of actions in Workday or connected systems when a business event fires. This is an internal event-driven architecture within Workday’s platform boundaries, not an outbound HTTP push to an external URL. Orchestrate handles the event routing, connector invocation, retry logic, and operational monitoring internally. For integrations where the destination system is reachable via a Workday Orchestrate connector, this gives you near-real-time event-driven behavior without needing to build external webhook infrastructure. For a practical walkthrough of Orchestrate-based event-driven automation in an onboarding context, including trigger configuration and cross-system connector design, the Workday Orchestrate implementation guide covers the production setup in full.

For integrations where the destination is a system not covered by Workday Orchestrate’s connector library, an iPaaS layer can implement virtual webhook behavior by polling Workday on your behalf and forwarding change events to your application as push notifications. This trades operational simplicity on the receiving side for added infrastructure complexity in the middleware layer.

For a detailed breakdown of how Workday’s REST API endpoints are structured across functional domains, including the authentication and delta-query patterns required for production polling implementations, the complete Workday REST API integration guide covers the architecture, OAuth token management, concurrent pagination, and rate limit handling at implementation depth.

How Infor ION Handles This: A Different Model

Infor ION uses a fundamentally different event delivery model that aligns more closely with the webhook paradigm than with polling. According to the Infor ION Development Guide, ION operates as a loosely coupled, event-driven middleware platform using Business Object Documents (BODs) as the standard integration interface. BODs are XML-structured messages based on the OAGIS schema standard, covering over 200 common business transaction types.

The ION integration model is a publish-and-subscribe architecture. When a business event occurs in an Infor application, such as an inventory transaction in Infor LN or a purchase order approval in Infor CloudSuite, the application publishes a BOD to its outbox. ION picks up the BOD, routes it through the configured connection points, and delivers it to the inbox of every subscribing application. Subscribing systems do not poll for changes. They receive BOD deliveries as they occur, driven by the event, not by a schedule.

This architecture provides several characteristics that polling cannot match. Delivery latency is bounded by the ION messaging pipeline rather than by a poll interval, which for most business events means near-real-time propagation across connected systems. Connection decoupling means a subscribing application’s unavailability does not affect other subscribers on the same ION connection point. And the BOD inbox/outbox model provides a natural persistent queue that buffers events during downstream system downtime and delivers them when the subscriber recovers.

The preferred integration mechanism for external systems connecting to ION is the Infor Application Connector, which uses this inbox/outbox model directly. When an external system cannot support the Application Connector, the File Connector is available as a fallback, but it introduces the risk of duplicate message delivery on timeout and lacks the reliability guarantees of the inbox/outbox pattern. For systems connecting via REST/JSON, the ION Messaging Service (IMS) connection point exposes an API that external systems can use to publish and subscribe to BOD events. The event management capabilities within Infor LN, and how they govern the publication of business events to ION, are covered in technical detail in the Infor LN event management architecture overview.

The Decision Framework: Webhook vs Polling

Given everything above, the pattern selection decision comes down to four variables.

Latency tolerance is the first variable. If your integration can accept data that is minutes or hours old, polling at an appropriate interval is simpler to implement, easier to debug, and more predictable under failure conditions. If your integration requires near-real-time propagation of changes, for example a hire event in Workday triggering immediate IAM provisioning or a payment event triggering immediate order status updates, the event-driven model is necessary.

Event frequency is the second variable. Low-frequency events, such as quarterly compensation reviews or monthly GL close extracts, are a poor fit for webhooks. The infrastructure overhead of endpoint management, signature verification, dead letter queuing, and reconciliation is disproportionate to the number of events arriving. Batch polling aligned to the business process schedule is the right pattern. High-frequency events, such as continuous IoT sensor readings, real-time inventory updates, or high-volume payment notifications, are a poor fit for polling. The combination of API rate limits and the wasted calls on empty responses makes polling architecturally unsuitable.

Platform capability is the third variable. As covered above, Workday does not support outbound webhooks natively. Designing an integration architecture that assumes Workday can push events to an external URL requires either Outbound Message Services configured against a specific business process, Workday Orchestrate for supported connectors, or a virtual webhook layer in an iPaaS. Building this assumption into a design without understanding its implications produces integrations that are harder to support than ones designed around Workday’s actual capabilities.

Consistency requirements under failure are the fourth variable. Polling integrations can recover naturally from source or destination downtime because the next scheduled poll will include any records that were missed during the outage window, provided the delta timestamp logic correctly captures the gap. Webhook integrations require explicit retry infrastructure, dead letter queues, and reconciliation jobs to achieve the same guarantee. If you are building on a platform or with a partner who will not implement those components, polling is the more reliable choice for your environment, even if it is less architecturally elegant.

The Hybrid Pattern: Webhooks as Triggers, APIs as Data Fetches

The most capable production integrations for high-stakes workflows use both patterns in sequence. A webhook delivers a lightweight event notification containing only the event type and key identifiers. On receipt, the integration issues a targeted API query against the source system to retrieve the full current record. The write to the destination system uses that API-fetched payload, not the webhook payload alone.

This hybrid model addresses the two principal weaknesses of pure webhook architectures: payload completeness and data freshness at processing time. Webhook payloads are point-in-time snapshots of the data as it existed when the event fired. If the record changed again between event firing and event processing, the webhook payload is stale. An API fetch at processing time guarantees you are writing the current state.

An order-to-cash workflow illustrates the pattern cleanly. An ecommerce platform fires a webhook when an order is created, containing the order ID and creation timestamp. The integration acknowledges receipt, queues the event, and then queries the order API for full line item, pricing, and customer data before writing to the ERP. When the logistics provider fires a webhook on shipment, the integration queries the carrier API for the tracking details before updating the CRM. Each step uses the webhook as a trigger and the API as the authoritative data source.

For enterprise environments where this hybrid pattern applies to Workday integrations, the custom integration development process that production-grade partners follow includes a latency requirements assessment and a data freshness specification before any architecture decisions are finalised. Integration patterns that are technically possible but architecturally inappropriate for the environment produce technical debt that compounds across every release cycle.

Security Controls That Apply to Both Patterns

Both polling and webhook integrations handle sensitive enterprise data and require the same baseline security controls, applied differently.

For polling integrations against Workday, every integration requires a dedicated Integration System User (ISU) configured with least-privilege domain-level permissions scoped to the specific data the integration accesses. ISUs should have dedicated, per-integration security groups, with session timeout set to zero and UI login disabled. OAuth 2.0 clients registered for REST API access require scope definitions that are tightly bounded to the API domains the integration needs. Sharing ISUs or OAuth clients across multiple integrations is a configuration that no audit-compliant environment should accept.

For webhook integrations, the security controls center on the receiving endpoint. All webhook endpoints must operate over HTTPS. Payload signature verification using HMAC-SHA256 against the shared secret must execute before any processing logic runs. Timestamps in webhook headers should be validated against a tight tolerance window, typically no more than five minutes, to prevent replay attacks where a captured valid delivery is retransmitted maliciously. Endpoint availability must be monitored with alerting, because a webhook consumer that goes dark drops events silently from the provider’s perspective if retry attempts are exhausted.

For both patterns in enterprise environments, credential rotation procedures, audit log retention, and transport encryption standards should be documented before the integration goes live, not discovered during the first security review.

Putting the Decision Into Practice

The polling versus webhook decision is not binary in production enterprise environments. It is a pattern selection per integration based on the source platform’s actual event delivery capabilities, the latency requirement of the receiving system, the failure recovery model your team can operationally support, and the rate limit characteristics of the API being consumed.

For Workday environments, the realistic architecture for most high-frequency event-driven requirements is Workday Orchestrate for supported connector destinations, Outbound Message Services for business process event notifications to external systems, and polling REST or RaaS for bulk synchronisation, historical loads, and complex queries. Native outbound webhooks are not part of Workday’s current architecture.

For Infor ION environments, the native BOD publish-subscribe model provides event-driven delivery by default, and integration architectures that route external systems through ION Application Connectors inherit those delivery guarantees without needing to build separate webhook infrastructure.

For organisations that need ongoing integration management and monitoring across multiple Workday and Infor integrations, the operational model needs to be defined at design time, not retrofitted after go-live. The architecture you choose now determines how much that operational model costs over the next five years.