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Event Grid Namespace – Webhook push subscription ignores maxEventsPerBatch and always shows 1 in portal

Guru Pasupathy 40 Reputation points
2026-01-07T00:12:19.81+00:00

I’m looking for an official clarification (or documentation link) regarding batching behavior for Azure Event Grid Namespace (EGNS) when using Push delivery with WebHook destinations.

Scenario

Azure Event Grid Namespace

Topic → Event Subscription

Delivery mode: Push

  • Destination: WebHook (APIM endpoint)

Event delivery schema: CloudEventSchemaV1_0

Subscription created via ARM / Terraform (azapi_resource)

I explicitly configure batching on the destination:

"maxEventsPerBatch": 5,
"preferredBatchSizeInKilobytes": 64

Deployment succeeds without validation errors.

Observed behavior

After creation, the Azure Portal always shows:

Max events per batch: 1

even though a higher value was provided during deployment.

Events are delivered with:

Content-Type: application/cloudevents+json

and never with:

application/cloudevents-batch+json

Even under burst publishing (multiple events sent very close together), delivery remains one event per HTTP request.

This suggests that for EGNS + WebHook push delivery, batching is either:

Not supported, or

Explicitly disabled / normalized to 1 by the service

Question

  • Is batching intentionally not supported for Event Grid Namespace push subscriptions with WebHook destinations or am I missing some other setting?

The general Event Grid documentation states batching is best-effort, but it does not appear to explicitly call out that EGNS WebHook push subscriptions will always behave as single-event delivery.

Azure Event Grid
Azure Event Grid

An Azure event routing service designed for high availability, consistent performance, and dynamic scale.

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  1. Pravallika KV 12,730 Reputation points Microsoft External Staff Moderator
    2026-01-07T04:49:59.74+00:00

    Hi @Guru Pasupathy ,

    Thanks for reaching out to Microsoft Q&A.

    Based on the scenario you've described, it seems that even after configuring batching with higher values, the Azure Portal displays the max events per batch as 1, and events are delivered individually rather than in batches.

    Here's what you can try:

    1. Confirm Batching Configuration: Ensure that your batch settings (both maxEventsPerBatch and preferredBatchSizeInKilobytes) are correctly set during the subscription creation via ARM/Terraform.
    2. Review Default Behavior: According to the Azure documentation, when using Webhooks as a destination, Event Grid defaults to sending events individually unless batching is explicitly enabled. If batching is set to OFF, it will only send one event per request.
    3. Check Event Grid Documentation: The documentation mentions that batching is not explicitly supported for every scenario with WebHooks and that it usually operates on a “best-effort” basis. However, it doesn't clearly specify if EGNS WebHook push subscriptions will always behave as single-event delivery. Therefore, double-check the documentation for any specific mentions regarding your setup.
    4. Debugging Metrics: You can monitor the metrics related to event delivery and look for any anomalies or metrics that suggest issues in the batching process:
    5. Explore Alternative Documentation: Review sections like Message push delivery and retry with namespace topics for details on the observed batching behavior.

    References:

    Hope this helps!

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