# Object Store watermarks between flow executions

*MuleSoft Developer Study Guide · Processing Records · Last updated October 28, 2026 · https://www.certifyforce.com/study-guide/mulesoft-developer/processing-records/object-store-watermarks-between-flow-executions*

Persist a watermark between Scheduler runs with the Object Store connector: Retrieve with a default value and a target, Store with `failIfPresent` and `failOnNullValue`, persistent versus transient stores, and what changes with Object Store v2 on CloudHub.

- Certification: Salesforce MuleSoft Developer
- Exam section: Processing Records
- Study guide: https://www.certifyforce.com/study-guide/mulesoft-developer

**Official exam objective:**

> Apply correct processors/syntax to persist data between flow executions.

## What the exam expects

- Choose the Object Store connector, not a variable, attribute or payload, to keep a value from one flow execution to the next.
- Configure Retrieve with `<os:default-value>` and `target`, and predict the payload, the variable and the store contents afterwards.
- Configure Store with `failIfPresent` and `failOnNullValue`, and name the error each default raises.
- Choose between the default store, a custom persistent store and a transient store.
- State what changes when a CloudHub app switches to Object Store v2.

Key terms:
- **Object store**: a key-value facility Mule uses to persist data for later retrieval.
- **Watermark**: the stored point where the next periodic synchronization should resume.
- **Default object store**: the persistent store every app has without configuration.
- **Object Store v2**: the CloudHub object store implementation selected in Runtime Manager.

## Key facts

| Fact | Detail | Source |
|---|---|---|
| Default object store | Persistent, available with no configuration | [Object Store Connector](https://docs.mulesoft.com/object-store-connector/latest/) |
| Transactions | Object stores do not support transactional access | [Object Store Connector](https://docs.mulesoft.com/object-store-connector/latest/) |
| Retrieve, missing key, no default | `OS:KEY_NOT_FOUND` | [Store and Retrieve Information in an Object Store Example](https://docs.mulesoft.com/object-store-connector/latest/object-store-to-store-and-retrieve) |
| Retrieve default value | Returned but not stored | [Store and Retrieve Information in an Object Store Example](https://docs.mulesoft.com/object-store-connector/latest/object-store-to-store-and-retrieve) |
| Retrieve without `target` | Value becomes the payload | [Store and Retrieve Information in an Object Store Example](https://docs.mulesoft.com/object-store-connector/latest/object-store-to-store-and-retrieve) |
| `failIfPresent` | Default `false` overwrites; `true` gives `OS:KEY_ALREADY_EXISTS` | [Store and Retrieve Information in an Object Store Example](https://docs.mulesoft.com/object-store-connector/latest/object-store-to-store-and-retrieve) |
| `failOnNullValue` | Default `true` gives `OS:NULL_VALUE`; `false` does nothing | [Store and Retrieve Information in an Object Store Example](https://docs.mulesoft.com/object-store-connector/latest/object-store-to-store-and-retrieve) |
| Transient store | Data does not survive a runtime crash | [Object Store Connector](https://docs.mulesoft.com/object-store-connector/latest/) |
| v1 to v2 switch | Data, including watermarks, does not carry over | [Object Store v2 Overview](https://docs.mulesoft.com/object-store/) |
| Object Store v2 entries | Unlimited; values up to 10 MB Base64-encoded | [Object Store v2 Overview](https://docs.mulesoft.com/object-store/) |
| On-premises access to v2 | Only through the Object Store REST API | [Object Store v2 Overview](https://docs.mulesoft.com/object-store/) |

## Check yourself

- What does Retrieve do when the key is missing and no default value is set?
- Why does the documented watermark Retrieve use `target`?
- When does a watermark Store fail on the second run?
- Why must watermarks be backed up before switching a CloudHub app to Object Store v2?

## Sources

- [Store and Retrieve Information in an Object Store Example](https://docs.mulesoft.com/object-store-connector/latest/object-store-to-store-and-retrieve)
- [Set Up Watermarks with an Object Store Example](https://docs.mulesoft.com/object-store-connector/latest/object-store-to-watermark)
- [Object Store Connector](https://docs.mulesoft.com/object-store-connector/latest/)
- [Store Application Data Using Object Stores](https://docs.mulesoft.com/mule-runtime/latest/mule-object-stores)
- [Object Store v2 Overview](https://docs.mulesoft.com/object-store/)
- [Mule Event Structure](https://docs.mulesoft.com/mule-runtime/latest/about-mule-event)

## About the full unit

The "Core concepts", "Exam traps" and "Worked scenario" sections of this unit, its 5 linked practice questions, and unlimited timed mock exams are included with the MuleSoft Developer pack (USD $19): https://www.certifyforce.com/practice-exams