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id: post/demiliani-com/14203
type: post
title: Why your Business Central job queue needs idempotent external effects when integrating external systems.
summary: Job queue entries that call external APIs risk duplicating actions when AL transactions roll back after an external call succeeds. Use the outbox row's SystemId as a stable idempotency key that the external system enforces to prevent duplicate exports, payments, or shipments on retry.
tier: community
language: en
tags:
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  - external api
  - idempotency
  - transaction handling
  - outbox pattern
  - error handling
  - http client
system: integration
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    title: Why your Business Central job queue needs idempotent external effects when integrating external systems.
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post_id: "14203"
source_id: demiliani-com
source_name: Stefano Demiliani
url: https://demiliani.com/2026/09/01/why-your-business-central-job-queue-needs-idempotent-external-effects-when-integrating-external-systems/
published_at: "2026-09-01T08:34:56.000Z"
author: Stefano Demiliani
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words: 1379
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code_objects_mentioned:
  - table Queued Export Bad
  - codeunit Queued Export Worker Bad
  - table Queued Export Good
  - codeunit Queued Export Worker Good
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# Why your Business Central job queue needs idempotent external effects when integrating external systems.

[Read the post](https://demiliani.com/2026/09/01/why-your-business-central-job-queue-needs-idempotent-external-effects-when-integrating-external-systems/) · Stefano Demiliani (Stefano Demiliani, MVP) · 2026-09-01 · 1379 words · tier community · reviewed (checked by Opus)

> Job queue entries that call external APIs risk duplicating actions when AL transactions roll back after an external call succeeds. Use the outbox row's SystemId as a stable idempotency key that the external system enforces to prevent duplicate exports, payments, or shipments on retry.

## Key points

- AL transaction rollback does not undo external API calls, creating a gap between database state and real-world side effects.
- The anti-pattern is calling external APIs before updating local records; if the local update fails, the row retries and sends the same request again.
- External systems must deduplicate requests using a stable idempotency key (like the outbox row's SystemId) that exists before the API call.
- Delete operations require treating certain response codes (like 404) as success and deleting the local row only after the external call confirms completion.
- Idempotency must be enforced by the external API itself; a local flag set after the call rolls back with everything else on failure.

## AL objects mentioned

As named in the post. A name that matches one object page by exact type and name links to it; the others stay as named.

- table "Queued Export Bad"
- codeunit "Queued Export Worker Bad"
- table "Queued Export Good"
- codeunit "Queued Export Worker Good"

Not found in BC28-30: table "Queued Export Bad", codeunit "Queued Export Worker Bad", table "Queued Export Good", codeunit "Queued Export Worker Good".

## Context

- Features: job queue retry, HTTP client, idempotency key, transaction rollback, outbox table, SystemId, external system integration

Source: Stefano Demiliani, community blog. Summary, key points and quotes are derived (CONTENT-NOTICE.md); read the original for the full text.