memgraph · gitbuda · Mar 25, 2026 · Mar 25, 2026 · Mar 27, 2026
@@ -1,3 +1,5 @@
+CLAUDE.md
+.claude/
 # next.js
 .next
 node_modules

@@ -32,6 +32,19 @@ filter, and convert relational data into a graph format.
 | **Implementation**  | Python     |
 | **Parallelism**     | sequential |
 
+<Callout type="info">
+When running multiple migrations against the same source, avoid repeating the `config` map in every call.
+Use [server-side parameters](/database-management/server-side-parameters) to store the connection config once
+and reference it as `$config` across all your queries:
+
+```cypher
+SET GLOBAL PARAMETER pg_config = {user: 'memgraph', password: 'password', host: 'localhost', database: 'demo_db'};
+
+CALL migrate.postgresql('users', $pg_config) YIELD row CREATE (u:User {id: row.id});
+CALL migrate.postgresql('orders', $pg_config) YIELD row CREATE (o:Order {id: row.id});
+```
+</Callout>
+
 ---
 
 ## Procedures

@@ -57,9 +57,9 @@ Offer the ability to compute embeddings during the preprocessing or retrieval
 stages.
 11. [`llm.complete`](/advanced-algorithms/available-algorithms/llm) function:
 Allows you to call any LLM under any given Cypher query.
-12. Server-side parameters: Could be used for many different things, but in this
-context, the parameters help you with managing configuration under any given
-query or pipeline.
+12. [Server-side parameters](/database-management/server-side-parameters): Could
+be used for many different things, but in this context, the parameters help you
+with managing configuration under any given query or pipeline.
 
 ## Question and Pipeline Types
 
@@ -107,4 +107,4 @@ exists, it synthesizes what is missing or not well-covered. Example use cases:
   - **Publishing**: *"I want to write a book, which important topics in this
   domain are not yet well covered in the existing literature?"*
 
-![atomic_graphrag_pipelines](/pages/ai-ecosystem/graph-rag/atomic-pipelines/atomic-graphrag-pipelines.png)
+![atomic_graphrag_pipelines](/pages/ai-ecosystem/graph-rag/atomic-pipelines/atomic-graphrag-pipelines.png)
@@ -60,5 +60,17 @@ production-ready clusters, scaling patterns, cross–data center deployments, an
 advanced architectures for low-latency or geographically distributed
 environments.
 
+## Upgrades & migration
+
+### [Upgrades](/database-management/upgrades)
+
+Plan Memgraph version upgrades, including standalone and HA clusters. Use the
+[version-specific guides](/database-management/upgrades/specific-versions) when
+moving between major releases.
+
+### [In-service software upgrade (ISSU) on Kubernetes](/clustering/high-availability/setup-ha-cluster-k8s#in-service-software-upgrade-issu)
+
+For HA on Kubernetes, Memgraph supports rolling upgrades with minimal downtime
+when you follow the ISSU procedure on the Helm chart setup page.
 
 <CommunityLinks/>
@@ -7,4 +7,5 @@ export default {
     "best-practices": "Best practices",
     "ha-commands-reference": "Reference commands",
     "ha-reference-architectures": "Reference architectures",
+    "migrating-to-v3-9-ha": "Migrating to v3.9 HA",
 }
@@ -279,6 +279,19 @@ The configuration value can be controlled using the query:
 SET COORDINATOR SETTING 'max_replica_read_lag' TO '10' ;
 ```
 
+### `deltas_batch_progress_size`
+
+Users can control how often REPLICAs report back to the MAIN that they're still processing the data (transactions, WALs, snapshots)
+the MAIN has sent to them. The default value is 100'000, which should be enough for most of your transactions.
+However, if processing 100'000 deltas takes more than 30s (because you're dealing with large deltas or you have older CPUs),
+you can set the configuration value `deltas_batch_progress_size` to a smaller value. This will avoid timeouts on REPLICAs so
+you won't see the query exception "At least one SYNC replica has not committed", but at the cost of lower throughput since REPLICAs
+will be sending in-progress messages to the MAIN more often.
+
+```
+SET COORDINATOR SETTING 'deltas_batch_progress_size' TO '50000';
+```
+
 ## Observability
 
 Monitoring cluster health is essential. Key metrics include:

@@ -14,12 +14,18 @@ Memgraph High Availability (HA) cluster.
 ## Cluster registration commands
 
 <Callout type="warning">
-**Important:** **All registration commands (adding coordinators and registering
-data instances) must be executed on the *same* coordinator.** You may choose any
+**Important:** You may choose any
 coordinator for the initial setup; it automatically becomes the leader. After
 setup, the choice no longer matters.
 </Callout>
 
+<Callout type="info">
+All queries can be run on any coordinator. If currently the coordinator is not a
+leader, the query will be automatically forwarded to the current leader and
+executed there. This is because the Raft protocol specifies that only the
+leader should accept changes in the cluster. 
+</Callout>
+
 ### `ADD COORDINATOR`
 
 Adds a coordinator to the cluster.
@@ -78,7 +84,6 @@ REMOVE COORDINATOR coordinatorId;
 
 {<h4 className="custom-header"> Behavior & implications </h4>}
 
-- Must be executed on the **leader** coordinator.
 - Leader coordinator **cannot** remove itself. To remove the leader, first
   trigger a leadership change.
 
@@ -90,7 +95,9 @@ REMOVE COORDINATOR 2;
 
 ### `UPDATE CONFIG`
 
-Updates the configuration of the data instance/coordinator in the cluster.
+Updates the configuration of the data instance/coordinator in the cluster. Use
+this command to update the DNS of your bolt servers, for example, when
+migrating to new load balancers.
 
 ```cypher
 UPDATE CONFIG FOR ( INSTANCE instanceName | COORDINATOR coordinatorServerId ) configsMap=configMap ;
@@ -106,7 +113,6 @@ of each instance.
 
 {<h4 className="custom-header"> Behavior & implications </h4>}
 
-- Must be executed on the **leader** coordinator.
 - Only bolt server can be updated.
 
 {<h4 className="custom-header"> Example </h4>}
@@ -294,8 +300,7 @@ SHOW INSTANCE;
 
 ### `SHOW REPLICATION LAG`
 
-Shows replication lag (in committed transactions) for all instances. Must be run
-on the **leader**.
+Shows replication lag (in committed transactions) for all instances.
 
 ```cypher
 SHOW REPLICATION LAG;
@@ -326,7 +331,5 @@ FORCE RESET CLUSTER STATE;
 
 {<h4 className="custom-header"> Implications </h4>}
 
-- Must be executed on the **leader** coordinator.
-
 
 <CommunityLinks/>
@@ -133,9 +133,19 @@ Below is a cleaned-up categorization.
 
 #### Coordinator → Coordinator RPCs
 
-| RPC                  | Purpose                                     | Description                                                                                                          |
-| -------------------- | ------------------------------------------- | -------------------------------------------------------------------------------------------------------------------- |
-| `ShowInstancesRpc` | Follower requests cluster state from leader | Sent by a follower coordinator to the leader coordinator when a user executes `SHOW INSTANCES` through the follower. |
+| RPC                      | Purpose                                      | Description                                                                                                                |
+| ------------------------ | -------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------- |
+| `ShowInstancesRpc`       | Follower requests cluster state from leader. | Sent by a follower coordinator to the leader coordinator when a user executes `SHOW INSTANCES` through the follower.       |
+| `AddCoordinatorRpc`      | Follower requests adding coordinator.        | Sent by a follower coordinator to the leader coordinator when a user executes `ADD COORDINATOR` through the follower.      |
+| `RemoveCoordinatorRpc`   | Follower requests removing coordinator.      | Sent by a follower coordinator to the leader coordinator when a user executes `REMOVE COORDINATOR` through the follower.   |
+| `RegisterInstanceRpc`    | Follower requests registering an instance.   | Sent by a follower coordinator to the leader coordinator when a user executes `REGISTER INSTANCE` through the follower.    |
+| `UnregisterInstanceRpc`  | Follower requests unregistering an instance. | Sent by a follower coordinator to the leader coordinator when a user executes `UNREGISTER INSTANCE` through the follower.  |
+| `SetInstanceToMainRpc`   | Follower requests updating MAIN instance.    | Sent by a follower coordinator to the leader coordinator when a user executes `SET INSTANCE TO MAIN` through the follower. |
+| `DemoteInstanceRpc`      | Follower requests demoting an instance.      | Sent by a follower coordinator to the leader coordinator when a user executes `DEMOTE INSTANCE` through the follower.      |
+| `UpdateConfigRpc`        | Follower requests updating config.           | Sent by a follower coordinator to the leader coordinator when a user executes `UPDATE CONFIG` through the follower.        |
+| `ForceResetRpc`          | Follower requests resetting cluster state.   | Sent by a follower coordinator to the leader coordinator when a user executes `FORCE RESET` through the follower.          |
+| `GetRoutingTableRpc`     | Follower requests a routing table.           | Sent by a follower coordinator to the leader coordinator when a user connects using `bolt+routing` through the follower.   |
+| `CoordReplicationLagRpc` | Follower requests replication lag info.      | Sent by a follower coordinator to the leader coordinator when a user executes `SHOW REPLICATION LAG` through the follower. |
 
 
 #### Coordinator → Data Instance RPCs

@@ -0,0 +1,42 @@
+---
+title: Migrating to v3.9 HA
+description: Learn about the required migration steps when upgrading a Memgraph high-availability cluster to version 3.9.
+---
+
+import { Callout } from 'nextra/components'
+import { Steps } from 'nextra/components'
+
+# Migrating to v3.9 HA
+
+Memgraph 3.9 includes a fix for a bug in how durability is handled on
+coordinators in a high-availability (HA) setup. Because of this fix, **all
+coordinator data directories must be cleaned and coordinators must be started
+fresh**.
+
+Data instances are not affected and can stay unchanged.
+
+<Callout type="warning">
+Upgrading to 3.9 **cannot be performed without downtime** if you are using a
+routing connection to connect to the currently writable instance. You can,
+however, keep using direct Bolt connections to data instances during this
+maintenance period.
+</Callout>
+
+<Steps>
+
+{<h3 className="custom-header">Clean coordinator data directories</h3>}
+
+Remove the data directories of all coordinators. If you are running Memgraph HA
+in Kubernetes, delete the coordinators' PVCs and PVs before the restart.
+
+{<h3 className="custom-header">Restart coordinators</h3>}
+
+Start all coordinators with the new Memgraph 3.9 version.
+
+{<h3 className="custom-header">Reconnect the cluster</h3>}
+
+After the coordinators are running, reconnect your cluster by executing
+`REGISTER INSTANCE` and `ADD COORDINATOR` queries for each data instance and
+coordinator respectively.
+
+</Steps>