How HC handles high-volume events

This page explains what happens under the hood and how to prepare when you know a spike is coming.

Dedicated per-customer queues

Every HC customer runs on an isolated event queue. A surge in one customer's order volume has no effect on processing for any other customer. If your Black Friday traffic spikes, that pressure is contained entirely within your queue.

Automatic scaling

HC scales horizontally in response to queue depth. As event volume increases, additional processing capacity is allocated automatically. You do not need to raise a support ticket or take any action — scaling is handled by the platform.

Where pressure actually builds

Most delays during high-volume periods are not caused by HC's queue — they come from the systems HC is posting into. Common bottlenecks:

• ERP rate limits — NetSuite and similar ERPs impose API call limits. HC respects these limits and queues events rather than dropping them, but processing will be slower if your ERP is at capacity.

• WMS import queues — warehouse systems often process fulfilment instructions in batches. A large spike may mean orders sit in the WMS queue for longer than usual before being picked up.

HC monitors these signals and retries automatically. Events are never lost.

Aggregation: batching events for file-based systems

For destinations that work with files rather than APIs — a 3PL collecting a CSV from an FTP server, for example — HC can aggregate events instead of sending each one individually. Events are combined into batches of a configured size: with a page size of 10, a job that produces 50 events results in 5 aggregated files of 10 events each.

Aggregation creates additional parent events that act as the containers for each batch. These parent events appear in the Control Panel like any other event and are chargeable as normal. Whether a destination sends in real time, on a schedule, or aggregated is part of your integration's design — ask HC if you are unsure which applies to a stream.

Retries and event durability

If a downstream system is temporarily unavailable or rate-limited, HC retries the event automatically using a backoff strategy. You can see the retry status of any event in the Control Panel. No events are silently dropped — everything either succeeds or appears in the failed events list for manual review or bulk resend.

Preparing for a known peak

If you have advance notice of a large spike — a product launch, a flash sale, or a seasonal campaign — there are a few things worth checking beforehand:

• Confirm all relevant streams are active and processing cleanly in the days before the event.

• Check with your ERP or WMS provider whether any API limits apply to your account and whether these can be temporarily raised.

• Verify that your error alerting is configured so you are notified promptly if any events fail.

• Make sure you know how to use the bulk resend feature in the Control Panel in case a batch of events needs to be replayed.

Let HC know in advance if you are expecting an unusually large spike. We can monitor more closely during the window and respond faster if anything unexpected comes up.