Square API Webhooks Are Being Delivered Multiple Times, Causing Duplicate Order Processing

[glenphillips]

Hi All,

I am working with the Square API for an application that processes order-related events, and I am experiencing an issue where the same webhook event sometimes appears to be delivered more than once. My application receives webhook notifications from Square and uses them to update the corresponding order information in its database. Most of the time, the process works as expected, but occasionally the same event is received again after the original notification has already been processed successfully. When this happens, my application may attempt to perform the same operation again, which can result in duplicate processing unless the application recognizes that the event has already been handled. I understand that webhook systems may retry deliveries when a response is delayed or an acknowledgment is not received, so I am not assuming that receiving the same event multiple times necessarily indicates a problem with Square itself. However, I want to make sure my integration handles these deliveries correctly and understand why the repeated notifications appear in some situations but not others.

I started investigating this after comparing the incoming webhook requests with the records stored in my application’s database. In the cases I have examined, the repeated notifications appear to refer to the same underlying event rather than separate actions initiated by a customer or another application process. The first notification is received and processed, but a subsequent delivery can arrive later and trigger the same processing logic again. Depending on the event type, repeating that logic can cause the application to attempt to create a duplicate record or repeat an update that has already been completed. I have checked the request timestamps and the event information available in the payload, but I would like to confirm the recommended way to identify a unique event across repeated deliveries. I am particularly interested in whether Square provides a stable event identifier that should be used for deduplication and whether there are any important differences between identifying a webhook delivery and identifying the underlying business event represented by that delivery.

Another aspect I am trying to understand is whether the repeated deliveries could be related to how quickly my application acknowledges incoming webhook requests. My current implementation performs some validation and database processing before returning an HTTP response, and I am wondering whether the acknowledgment might occasionally take longer than expected when the database is busy. If Square does not receive the expected successful response within its delivery window, I understand that it may retry the notification, even if my application has already started processing the original request. I have not yet confirmed that this is the cause, because the repeated deliveries do not appear to follow an identical timing pattern every time. I would appreciate advice on how to compare the webhook delivery timestamps with the application’s request logs and response codes to determine whether retries are being triggered by delayed acknowledgments, temporary network failures, or another delivery condition. I want to establish what actually happened during each repeated delivery rather than treating every duplicate as evidence of a Square-side problem.

I am also considering how to structure the processing flow so that receiving the same event multiple times cannot cause the underlying operation to happen more than once. At the moment, the application checks the incoming event and then proceeds with the relevant database operation, but I want to make sure that this check remains reliable if two deliveries arrive close together or if the original processing is interrupted before completion. Simply checking whether an event has been seen before may not be sufficient if the check and the database update are separate operations that can overlap. I would like to know whether a database-backed event ledger, a unique constraint on the event identifier, or a transaction-based approach is generally recommended for Square webhook integrations. I also want to understand how to handle a situation where the application has completed its business operation but fails before returning a successful HTTP response, because a retry in that situation should not repeat the operation. My goal is to make the integration safe when deliveries are repeated without discarding legitimate new events that happen to concern the same order.

For further troubleshooting, I can collect sanitized webhook payloads, event identifiers, request timestamps, HTTP response codes, processing durations, and relevant application logs from cases where a notification was delivered more than once. I would appreciate guidance on which fields in the Square webhook payload should be recorded for reliable event tracking and which information is most useful when investigating delivery retries. I would also like to know whether Square provides a dashboard or API endpoint where I can inspect delivery attempts and determine whether a repeated notification resulted from a retry. If there are specific requirements for validating webhook signatures, acknowledging requests, or handling the delivery lifecycle, I would be grateful for recommendations that apply to the current Square API. I am trying to keep the integration straightforward and avoid adding unnecessary complexity, but I also want to make sure that a temporary delay or repeated delivery cannot result in duplicate order processing.

Has anyone working with the Square API encountered this type of repeated webhook delivery and found a reliable way to make event processing idempotent? I would appreciate advice on the recommended sequence for receiving a notification, validating it, recording its event identifier, acknowledging the delivery, and processing the corresponding business operation safely. I am especially interested in best practices for avoiding duplicate database changes when the same event is delivered again or when two deliveries arrive almost simultaneously. I understand that webhook consumers should generally be designed to tolerate retries, but I would like to confirm the most appropriate implementation pattern for Square rather than relying on assumptions about delivery timing. Any suggestions for diagnosing the cause of repeated deliveries and implementing reliable deduplication would be helpful, particularly if there are Square-specific details that developers should consider when building a production integration. Sorry for long post!

[DanielWilson]

The safest approach is to store each webhook’s event ID with a unique database constraint and make processing idempotent. Acknowledge requests quickly, then handle the work asynchronously to reduce retries caused by slow responses.

[glenphillips]

@glenphillips

I am working with the Square API for an application that processes order-related events, and I am experiencing an issue where the same webhook event sometimes appears to be delivered more than once. My application receives webhook notifications from Square and uses them to update the corresponding order information in its database. Most of the time, the process works as expected, but occasionally the same event is received again after the original notification has already been processed successfully. When this happens, my application may attempt to perform the same operation again, which can result in duplicate processing unless the application recognizes that the event has already been handled. I understand that webhook systems may retry deliveries when a response is delayed or an acknowledgment is not received, so I am not assuming that receiving the same event multiple times necessarily indicates a problem with Square itself. However, I want to make sure my integration handles these deliveries correctly and understand why the repeated notifications appear in some situations but not others.

I started investigating this after comparing the incoming webhook requests with the records stored in my application’s database. In the cases I have examined, the repeated notifications appear to refer to the same underlying event rather than separate actions initiated by a customer or another application process. The first notification is received and processed, but a subsequent delivery can arrive later and trigger the same processing logic again. Depending on the event type, repeating that logic can cause the application to attempt to create a duplicate record or repeat an update that has already been completed. I have checked the request timestamps and the event information available in the payload, but I would like to confirm the recommended way to identify a unique event across repeated deliveries. I am particularly interested in whether Square provides a stable event identifier that should be used for deduplication and whether there are any important differences between identifying a webhook delivery and identifying the underlying business event represented by that delivery.

Another aspect I am trying to understand is whether the repeated deliveries could be related to how quickly my application acknowledges incoming webhook requests. My current implementation performs some validation and database processing before returning an HTTP response, and I am wondering whether the acknowledgment might occasionally take longer than expected when the database is busy. If Square does not receive the expected successful response within its delivery window, I understand that it may retry the notification, even if my application has already started processing the original request. I have not yet confirmed that this is the cause, because the repeated deliveries do not appear to follow an identical timing pattern every time. I would appreciate advice on how to compare the webhook delivery timestamps with the application’s request logs and response codes to determine whether retries are being triggered by delayed acknowledgments, temporary network failures, or another delivery condition. I want to establish what actually happened during each repeated delivery rather than treating every duplicate as evidence of a Square-side problem.

I am also considering how to structure the processing flow so that receiving the same event multiple times cannot cause the underlying operation to happen more than once. At the moment, the application checks the incoming event and then url proceeds with the relevant database operation, but I want to make sure that this check remains reliable if two deliveries arrive close together or if the original processing is interrupted before completion. Simply checking whether an event has been seen before may not be sufficient if the check and the database update are separate operations that can overlap. I would like to know whether a database-backed event ledger, you can check url as well, a unique constraint on the event identifier, or a transaction-based approach is generally recommended for Square webhook integrations. I also want to understand how to handle a situation where the application has completed its business operation but fails before returning a successful HTTP response, because a retry in that situation should not repeat the operation. My goal is to make the integration safe when deliveries are repeated without discarding legitimate new events that happen to concern the same order.

For further troubleshooting, I can collect sanitized webhook payloads, event identifiers, request timestamps, HTTP response codes, processing durations, and relevant application logs from cases where a notification was delivered more than once. I would appreciate guidance on which fields in the Square webhook payload should be recorded for reliable event tracking and which information is most useful when investigating delivery retries. I would also like to know whether Square provides a dashboard or API endpoint where I can inspect delivery attempts and determine whether a repeated notification resulted from a retry. If there are specific requirements for validating webhook signatures, acknowledging requests, or handling the delivery lifecycle, I would be grateful for recommendations that apply to the current Square API. I am trying to keep the integration straightforward and avoid adding unnecessary complexity, but I also want to make sure that a temporary delay or repeated delivery cannot result in duplicate order processing.

Has anyone working with the Square API encountered this type of repeated webhook delivery and found a reliable way to make event processing idempotent? I would appreciate advice on the recommended sequence for receiving a notification, validating it, recording its event identifier, acknowledging the delivery, and processing the corresponding business operation safely. I am especially interested in best practices for avoiding duplicate database changes when the same event is delivered again or when two deliveries arrive almost simultaneously. I understand that webhook consumers should generally be designed to tolerate retries, but I would like to confirm the most appropriate implementation pattern for Square rather than relying on assumptions about delivery timing. Any suggestions for diagnosing the cause of repeated deliveries and implementing reliable deduplication would be helpful, particularly if there are Square-specific details that developers should consider when building a production integration. Sorry for long post!!

Thanks for the suggestion. Using a unique database constraint on the webhook event ID sounds like a reliable way to prevent the same event from being processed twice, especially if two deliveries arrive close together. I also agree that acknowledging the request quickly and moving the actual processing to a background job could help reduce retries caused by slow database operations. I’m interested in how to handle the situation where the event ID is recorded successfully but the background job fails before completing the order update.

[zacstlouis]

Square delivers webhooks at least once, so your handler needs to handle duplicates. Deduplicate on event_id. Every delivery of a given event, retries included, has the same event_id. A separate order.updated for the same order gets a new event_id, and you should process it, because it can carry a real state change.

• Insert event_id into a table with a UNIQUE constraint. If the insert conflicts, return 200 and stop. The constraint is what makes this safe when two deliveries overlap. A separate “have I seen this?” check isn’t.
• Return 200 right away, then do the business work asynchronously from the ledger or a queue.
• Write the business change and mark the event “processed” in the same transaction. If you crash after committing but before responding, the retry finds the event already processed and does nothing.
• Events can arrive out of order. Retrieve the order and act on its current state/version instead of trusting the order events arrived in.

I’m interested in how to handle the situation where the event ID is recorded successfully but the background job fails before completing the order update.

If you store the event object and the id you can retry on your end as many times as you need and not have to worry about the webhook still hitting your service. If a new update webhook comes in tied to the same record of the failing one you would want to move on to processing the new one instead of the old event but this depends on what you are actually doing on your end.