diff --git a/pom.xml b/pom.xml
index d84bb93..998935e 100644
--- a/pom.xml
+++ b/pom.xml
@@ -34,6 +34,11 @@
   </repositories>
 
   <dependencies>
+    <dependency>
+      <groupId>org.mongodb</groupId>
+      <artifactId>bson</artifactId>
+      <version>5.0.0</version>
+    </dependency>
     <dependency>
       <groupId>org.rocksdb</groupId>
       <artifactId>rocksdbjni</artifactId>
@@ -236,7 +241,7 @@
                 <buildArg>-H:IncludeResources=it/cavallium/rockserver/core/resources/build.properties</buildArg>
                 <buildArg>-H:DynamicProxyConfigurationFiles=proxy-config.json</buildArg>
                 <buildArg>-H:ReflectionConfigurationFiles=reflect-config.json</buildArg>
-                <buildArg>--initialize-at-run-time=org.rocksdb.RocksDB,org.rocksdb.RocksObject</buildArg>
+                <buildArg>--initialize-at-run-time=org.rocksdb.RocksDB,org.rocksdb.RocksObject,org.rocksdb.RocksDBException</buildArg>
                 <!--<buildArg>_-no-fallback</buildArg>-->
                 <buildArg>--gc=G1</buildArg>
                 <buildArg>--link-at-build-time</buildArg>
diff --git a/src/main/java/it/cavallium/rockserver/core/Migrate.java b/src/main/java/it/cavallium/rockserver/core/Migrate.java
new file mode 100644
index 0000000..9e6a5e2
--- /dev/null
+++ b/src/main/java/it/cavallium/rockserver/core/Migrate.java
@@ -0,0 +1,96 @@
+package it.cavallium.rockserver.core;
+
+import it.cavallium.rockserver.core.common.api.ColumnSchema;
+import it.cavallium.rockserver.core.common.api.RocksDB;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.time.Duration;
+import java.time.Instant;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
+import org.apache.thrift.TApplicationException;
+import org.apache.thrift.TException;
+import org.apache.thrift.protocol.TBinaryProtocol;
+import org.apache.thrift.transport.TSocket;
+import org.apache.thrift.transport.layered.TFramedTransport;
+import org.bson.BasicBSONEncoder;
+import org.bson.BasicBSONObject;
+import org.bson.Document;
+
+public class Migrate {
+
+	public static void main(String[] args) throws TException, IOException {
+
+		// Tunables
+		String n = "401";
+		var columnName = "peers_dtg-slave-" + n;
+		var columnSchema = new ColumnSchema(List.of(Long.BYTES), List.of(), true);
+		//
+
+		var transport = new TFramedTransport(new TSocket("10.0.0.9", 5332));
+		transport.open();
+
+		var jo = Document.parse("{\"data\": " + Files.readString(Path.of("/tmp/export/" + columnName + ".json")) + "}");
+
+		List<Document> documents = (List<Document>) jo.get("data");
+		jo = null;
+		System.gc();
+		System.out.println("Read json file");
+		var it = documents.iterator();
+		List<Map.Entry<Long, BasicBSONObject>> documentMap = new ArrayList<>();
+		while (it.hasNext()) {
+			var document = it.next();
+			var obj = new BasicBSONObject();
+			var id = ((Number) document.get("id")).longValue();
+			var accessHash = ((Number) document.get("access_hash")).longValue();
+			var peerType = ((String) document.get("type"));
+			var username = ((String) document.get("username"));
+			var phoneNumber = ((String) document.get("phone_number"));
+			var lastUpdateOn = ((Number) document.get("last_update_on")).longValue();
+			obj.put("access_hash", accessHash);
+			obj.put("peer_type", peerType);
+			obj.put("username", username);
+			obj.put("phone_number", phoneNumber);
+			obj.put("last_update_on", lastUpdateOn);
+			documentMap.add(Map.entry(id, obj));
+		}
+		documents = null;
+		System.gc();
+		System.out.println("parsed documents");
+		var protocol = new TBinaryProtocol(transport);
+		var client = new RocksDB.Client(protocol);
+		long columnId;
+
+		long tmpColumnId;
+		try {
+			tmpColumnId = client.getColumnId(columnName);
+		} catch (TApplicationException ex) {
+			tmpColumnId = client.createColumn(columnName, columnSchema);
+		}
+		columnId = tmpColumnId;
+		var encoder = new BasicBSONEncoder();
+		long nn = 0;
+		long total = documentMap.size();
+		var initTime = Instant.now();
+		for (Entry<Long, BasicBSONObject> longDocumentEntry : documentMap) {
+			ByteBuffer bb = ByteBuffer.allocate(Long.BYTES);
+			bb.asLongBuffer().put(longDocumentEntry.getKey());
+			var valueArray = encoder.encode(longDocumentEntry.getValue());
+			var valueBuf = ByteBuffer.wrap(valueArray);
+			client.putFast(0, columnId, List.of(bb), valueBuf);
+			if (nn > 0 && nn % 10_000 == 0) {
+				var endTime = Instant.now();
+				var dur = Duration.between(initTime, endTime);
+				System.out.printf("Written %d/%d elements... %.2f, speed: %.2fHz%n", nn, total, ((nn * 100d) / total),  nn / (dur.toMillis() / 1000d));
+			}
+			nn++;
+		}
+		var endTime = Instant.now();
+		var dur = Duration.between(initTime, endTime);
+		if (total > 0) System.out.printf("Took %s, speed: %.2fHz%n", dur, total / (dur.toMillis() / 1000d));
+	}
+}
diff --git a/src/main/java/module-info.java b/src/main/java/module-info.java
index 918e4f1..c31ca7b 100644
--- a/src/main/java/module-info.java
+++ b/src/main/java/module-info.java
@@ -9,6 +9,7 @@ module rockserver.core {
 	requires it.unimi.dsi.fastutil;
 	requires org.apache.thrift;
 	requires org.slf4j;
+	requires org.mongodb.bson;
 
 	exports it.cavallium.rockserver.core.client;
 	exports it.cavallium.rockserver.core.common;