Add blog post about Khepri being/becoming the default metadata store.

blog/2025-07-01-khepri-default/index.md

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+---
+title: "The Roadmap for Making Khepri the Default Metadata Store in RabbitMQ"
+tags: ["khepri"]
+authors: [mgary]
+---
+
+Khepri, the new Raft-based RabbitMQ [metadata store](https://www.rabbitmq.com/docs/metadata-store), became fully supported with RabbitMQ 4.0.
+Starting with the next release series, RabbitMQ 4.2, we consider Khepri to be mature enough to become the default metadata store,
+especially given its substantial data safety and recovery improvements over Mnesia.
+
+We have performed [a number of benchmarks](#khepri-performance-improvements), showing significant performance improvements in many metadata operations.
+
+<!-- truncate -->
+
+## Khepri Feature Flag now stable
+
+The `khepri_db` feature flag has now been upgraded to `Stable`, meaning it will now be enabled when running the command `rabbitmqctl enable_feature_flag all`,
+which should be done after every successful version upgrade.
+
+Starting with version 4.2, all RabbitMQ clusters will be strongly recommended to adopt Khepri by enabling the `khepri_db` feature flag. This feature flag will
+**likely become mandatory** for upgrading from 4.2 onwards.
+
+While the final decision depends on the community feedback, we expect that starting with RabbitMQ 4.3,
+the `khepri_db` feature flag will [graduate](https://www.rabbitmq.com/docs/feature-flags#graduation) to be `Required`.
+
+### Feature Flag Subsystem
+
+The RabbitMQ [feature flag subsystem](https://www.rabbitmq.com/docs/feature-flags) was recently improved by introducing a new category of feature flags known as `Soft Required`.
+If a feature flag is `Soft Required` starting from version `N`, it is automatically enabled once all RabbitMQ nodes are upgraded to version `N` of RabbitMQ.
+This is a change from the previous behavior of `Required`, where a feature flag that became required in version `N` of RabbitMQ must be enabled before upgrading to version `N`.
+
+It remains best practice to enable feature flags as soon as they become `Stable`, generally immediately after a successful upgrade by running the command `rabbitmqctl enable_feature_flag all`.
+Nonetheless, we view the introduction of `Soft Required` feature flags as an improvement in user experience,
+as any required feature flags not already enabled will be automatically enabled when required.
+
+## Khepri Performance Improvements
+
+The benchmarks below were performed on a 3 node cluster running on Kubernetes
+
+### 1000 queues, each with 100 bindings
+| benchmark                  | mnesia | khepri |
+| -------------------------- | ------ | ------ |
+| import                     | 446 s  | 51 s   |
+| re-import                  | 16 s   | 46 s   |
+| stop_app                   | 1.6 s  | 1.7 s  |
+| start_app                  | 22 s   | 4.3 s  |
+| rolling cluster restart    | 108 s  | 67 s   |
+| mnesia to khepri migration | 12.7 s |        |
+
+### 1000 Vhosts
+| benchmark                  | mnesia | khepri |
+| -------------------------- | ------ | ------ |
+| import                     | 284 s  | 21 s   |
+| re-import                  | 2.2 s  | 2.2 s  |
+| stop_app                   | 2.6 s  | 2.4 s  |
+| start_app                  | 419 s  | 16 s   |
+| rolling cluster restart    | 1447 s | 106 s  |
+| mnesia to khepri migration | 5.5 s  |        |
+
+### 100,000 Classic Queues
+| benchmark                  | mnesia | khepri |
+| -------------------------- | ------ | ------ |
+| import                     | 76 s   | 76 s   |
+| re-import                  | 5.4 s  | 5.3 s  |
+| stop_app                   | 13 s   | 6 s    |
+| start_app                  | 26 s   | 40 s   |
+| rolling cluster restart    | 185 s  | 307 s  |
+| mnesia to khepri migration | 9.7 s  |        |
+
+### 10,000 Quorum Queues
+| benchmark                  | mnesia | khepri |
+| -------------------------- | ------ | ------ |
+| import                     | 49 s   | 46 s   |
+| re-import                  | 1.9 s  | 1.8 s  |
+| stop_app                   | 1.9 s  | 1.7 s  |
+| start_app                  | 44 s   | 44 s   |
+| rolling cluster restart    | 285 s  | 267 s  |
+| mnesia to khepri migration | 4.7 s  |        |
+
+### 1,000 Streams
+| benchmark                  | mnesia | khepri |
+| -------------------------- | ------ | ------ |
+| import                     | 3.5 s  | 1.2 s  |
+| re-import                  | 1.6 s  | 1.2 s  |
+| stop_app                   | 1.9 s  | 1.2 s  |
+| start_app                  | 2.5 s  | 2.3 s  |
+| rolling cluster restart    | 56 s   | 55 s   |
+| mnesia to khepri migration | 5 s    |        |