What Are Virtual Webhooks? How They Differ From Sync-Based Webhooks
December 15, 2025
[Virtual webhooks](/blog/unlock_real_time_data_with_virtual_webhooks) provide event delivery for integrations that don't support native webhooks.
Instead of requiring your application to poll APIs for changes, the integration layer detects changes and delivers them as webhook events.
This is not how all 'webhooks' work.
Some systems emit events when a change is detected. Others emit events after data has been synced into a stored copy.
That distinction affects latency, API usage, and how much infrastructure your team owns.
For a broader comparison of how unified API platforms implement virtual webhooks vs sync-based notification systems, see: Which Unified API Platforms Support Virtual Webhooks vs Sync-Based Notifications
Native webhooks (baseline)
Native webhooks are emitted by the source system.
- The source API detects a change
- An event is sent immediately
- Your application processes it
This is the simplest model, but coverage is limited. Many APIs do not support webhooks consistently across objects.
Virtual webhooks (detect → deliver)
Virtual webhooks provide event delivery when native webhooks are not available.
Under the hood:
- the integration layer polls the source API
- detects changes using timestamps, cursors, or diffs
- delivers a webhook event when a change is detected
From your application's perspective:
- you subscribe once
- you receive events
- you do not manage polling infrastructure
Polling still exists—it is handled inside the integration layer instead of your application.
Virtual webhooks replace application-level polling with centralized change detection.
Sync-based webhooks (sync → notify)
Some platforms use a different model.
- data is retrieved on a schedule
- records are written into a vendor-managed store
- webhook events are emitted after the sync completes
These events are tied to batch updates, not real-time change detection.
In most cases:
- the webhook signals that data changed
- your application retrieves updated records separately
The key difference: data vs signal
The core distinction is what the webhook delivers and when it is generated.
| Aspect | Virtual webhooks | Sync-based webhooks |
|---|---|---|
| Trigger | Change detection | Sync completion |
| Payload | Often includes updated data | Often a signal only |
| Follow-up API call | Often not required | Often required |
| Data storage | Not required | Required |
| Latency bound by | Detection interval | Sync schedule + storage lag |
Virtual webhooks are generated from detected changes in the source system.
Sync-based webhooks are generated from changes in a stored copy.
Why this difference matters
API usage
Sync-based systems often require:
- one event
- one or more follow-up API calls
Virtual webhooks can deliver updated records in the initial event, reducing additional reads.
Latency
Sync-based systems introduce delay from:
- sync frequency
- processing queues
- storage updates
Virtual webhooks are bounded by how frequently changes are detected.
System design
Sync-based systems require handling:
- sync state
- replica consistency
- timing mismatches between sync and events
Virtual webhooks reduce this to a single event stream based on detected changes.
Data handling
Sync-based systems depend on storing customer data in a vendor-managed database.
Virtual webhook systems can operate without storing customer records, retrieving data directly from the source API when events are generated.
How Unified implements virtual webhooks
Unified uses a change-detection model to deliver webhook events without storing customer data.
- polling and change detection are handled internally
- events are generated from source API changes
- additional data is retrieved directly from the source API
This avoids:
- maintaining a replicated data layer
- cache-based inconsistencies
- managing sync jobs
The result is a consistent event model across integrations, regardless of whether native webhooks exist.
When virtual webhooks are the right fit
Virtual webhooks are useful when:
- the integration does not provide native webhooks
- your product depends on timely updates
- you want to avoid building polling infrastructure
- you want to avoid managing sync pipelines or stored replicas
Key takeaway
Not all webhooks are event-driven in the same way.
- Virtual webhooks detect changes and deliver events
- Sync-based webhooks notify after batch updates
The difference is whether your system receives data when it changes, or a signal that requires additional retrieval.
That distinction determines latency, architecture, and how much integration logic your team owns.