# 441 Queue Deduplication 71c584da

> Deduplicate Queued Workflows

- Skill: `tools-only/441-queue-deduplication-71c584da` (Agent Skill, multi-file: 3 files)
- Install (CLI): `npx skillmds@latest add tools-only/441-queue-deduplication-71c584da`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tools-only/441-queue-deduplication-71c584da/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Productivity
- Author: tools-only (https://skillmd.com/u/tools-only)
- Updated: 2026-09-22
- Page: https://skillmd.com/skills/tools-only/441-queue-deduplication-71c584da

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## Deduplicate Queued Workflows

Use deduplication IDs to ensure only one workflow with a given ID is active in a queue at a time.

**Incorrect (duplicate workflows possible):**

```python
queue = Queue("user_tasks")

@app.post("/process/{user_id}")
def process_for_user(user_id: str):
    # Multiple requests = multiple workflows for same user!
    queue.enqueue(process_workflow, user_id)
```

**Correct (deduplicated by user):**

```python
from dbos import Queue, SetEnqueueOptions
from dbos import error as dboserror

queue = Queue("user_tasks")

@app.post("/process/{user_id}")
def process_for_user(user_id: str):
    with SetEnqueueOptions(deduplication_id=user_id):
        try:
            handle = queue.enqueue(process_workflow, user_id)
            return {"workflow_id": handle.get_workflow_id()}
        except dboserror.DBOSQueueDeduplicatedError:
            return {"status": "already processing"}
```

Deduplication behavior:
- If a workflow with the same deduplication ID is `ENQUEUED` or `PENDING`, new enqueue raises `DBOSQueueDeduplicatedError`
- Once the workflow completes, a new workflow with the same ID can be enqueued
- Deduplication is per-queue (same ID can exist in different queues)

Use cases:
- One active task per user
- Preventing duplicate job submissions
- Rate limiting by entity

Reference: [Queue Deduplication](https://docs.dbos.dev/python/tutorials/queue-tutorial#deduplication)