diff --git a/step-controller/step-controller-server/src/main/java/step/core/imports/converter/ArtefactsToPlans.java b/step-controller/step-controller-server/src/main/java/step/core/imports/converter/ArtefactsToPlans.java
index a20b8eae0..03f62cfce 100644
--- a/step-controller/step-controller-server/src/main/java/step/core/imports/converter/ArtefactsToPlans.java
+++ b/step-controller/step-controller-server/src/main/java/step/core/imports/converter/ArtefactsToPlans.java
@@ -115,7 +115,7 @@ protected Document migrateArtefactToPlan(AtomicInteger successCount, AtomicInteg
 			
 			Document plan = new Document();
 			
-			plan.put(AbstractIdentifiableObject.ID, artefactIdToPlanId.get(t.getId()));
+			plan.put(AbstractIdentifiableObject.ID, artefactIdToPlanId.get(t.getId().toString()));
 			plan.put("attributes", attributes);
 			plan.put("root", migrateArtefact(t));
 			plan.put("visible", visiblePlan);
diff --git a/step-core/src/main/java/step/core/entities/EntityDependencyTreeVisitor.java b/step-core/src/main/java/step/core/entities/EntityDependencyTreeVisitor.java
index b6d98b125..ffef005f7 100644
--- a/step-core/src/main/java/step/core/entities/EntityDependencyTreeVisitor.java
+++ b/step-core/src/main/java/step/core/entities/EntityDependencyTreeVisitor.java
@@ -28,7 +28,9 @@ public class EntityDependencyTreeVisitor {
 	private static final Logger logger = LoggerFactory.getLogger(EntityDependencyTreeVisitor.class);
 	private final EntityManager entityManager;
 	private final ObjectPredicate objectPredicate;
-	private final Map<Class<?>, BeanInfo> beanInfoCache = new ConcurrentHashMap<>();
+	// Declared as static for performance reasons. In the current implementation, this class gets instantiated quite often
+	// TODO declare it as non-static to avoid potential leaks
+	private static final Map<Class<?>, BeanInfo> beanInfoCache = new ConcurrentHashMap<>();
 
 	public EntityDependencyTreeVisitor(EntityManager entityManager, ObjectPredicate objectPredicate) {
 		super();
diff --git a/step-core/src/main/java/step/core/imports/ImportContext.java b/step-core/src/main/java/step/core/imports/ImportContext.java
index a3aa45af5..d8319cf85 100644
--- a/step-core/src/main/java/step/core/imports/ImportContext.java
+++ b/step-core/src/main/java/step/core/imports/ImportContext.java
@@ -18,6 +18,12 @@
  ******************************************************************************/
 package step.core.imports;
 
+import ch.exense.commons.io.FileHelper;
+import step.core.Version;
+import step.core.collections.CollectionFactory;
+import step.core.collections.inmemory.InMemoryCollectionFactory;
+import step.resources.LocalResourceManagerImpl;
+
 import java.io.File;
 import java.io.IOException;
 import java.util.HashMap;
@@ -25,11 +31,6 @@
 import java.util.Map;
 import java.util.Set;
 
-import step.core.collections.filesystem.FilesystemCollectionFactory;
-import ch.exense.commons.io.FileHelper;
-import step.core.Version;
-import step.resources.LocalResourceManagerImpl;
-
 public class ImportContext implements AutoCloseable {
 
 	private final ImportConfiguration importConfiguration;
@@ -40,8 +41,7 @@ public class ImportContext implements AutoCloseable {
 	private final File workFolder;
 	private final LocalResourceManagerImpl localResourceMgr;
 
-	private final File tempWorkspace;
-	private final FilesystemCollectionFactory tempCollectionFactory;
+	private final CollectionFactory tempCollectionFactory;
 
 	private final Map<String, String> references = new HashMap<String, String>();
 	private final Map<String, String> newToOldReferences = new HashMap<String, String>();
@@ -51,8 +51,7 @@ public ImportContext(ImportConfiguration importConfiguration) throws IOException
 		super();
 		this.importConfiguration = importConfiguration;
 
-		tempWorkspace = FileHelper.createTempFolder();
-		tempCollectionFactory = new FilesystemCollectionFactory(tempWorkspace);
+		tempCollectionFactory = new InMemoryCollectionFactory(null);
 		workFolder = FileHelper.createTempFolder("step-import");
 		localResourceMgr = new LocalResourceManagerImpl(workFolder);
 	}
@@ -81,7 +80,7 @@ public LocalResourceManagerImpl getLocalResourceMgr() {
 		return localResourceMgr;
 	}
 
-	public FilesystemCollectionFactory getTempCollectionFactory() {
+	public CollectionFactory getTempCollectionFactory() {
 		return tempCollectionFactory;
 	}
 
@@ -108,6 +107,5 @@ public File getWorkFolder() {
 	@Override
 	public void close() throws Exception {
 		FileHelper.deleteFolder(workFolder);
-		FileHelper.deleteFolder(tempWorkspace);
 	}
 }
diff --git a/step-core/src/main/java/step/core/imports/ImportManager.java b/step-core/src/main/java/step/core/imports/ImportManager.java
index 61884088c..b282d9bb8 100644
--- a/step-core/src/main/java/step/core/imports/ImportManager.java
+++ b/step-core/src/main/java/step/core/imports/ImportManager.java
@@ -32,9 +32,9 @@
 import step.core.accessors.Accessor;
 import step.core.accessors.DefaultJacksonMapperProvider;
 import step.core.collections.Collection;
+import step.core.collections.CollectionFactory;
 import step.core.collections.Document;
 import step.core.collections.Filters;
-import step.core.collections.filesystem.FilesystemCollectionFactory;
 import step.core.entities.Entity;
 import step.core.entities.EntityManager;
 import step.migration.MigrationManager;
@@ -124,7 +124,7 @@ public ImportResult importAll(ImportConfiguration importConfig) throws Exception
 
 	private void importEntitiesFromTemporaryCollection(ImportConfiguration importConfig, ImportContext importContext, List<String> entityNames) {
 		// Perform migration tasks on temporary collections
-		final FilesystemCollectionFactory tempCollectionFactory = importContext.getTempCollectionFactory();
+		final CollectionFactory tempCollectionFactory = importContext.getTempCollectionFactory();
 		migrationManager.migrate(tempCollectionFactory, importContext.getVersion(), Version.getCurrentVersion());
 
 		// Replace IDs of all entities if overwriting is disabled
@@ -172,7 +172,7 @@ private String importEntitiesToTemporaryCollection(ImportConfiguration importCon
 		Entity<?, ?> entityByName = entityManager.getEntityByName(name);
 		boolean skip = skipEntityType(importConfig.getEntitiesFilter(), name);
 
-		FilesystemCollectionFactory tempCollectionFactory = importContext.getTempCollectionFactory();
+		CollectionFactory tempCollectionFactory = importContext.getTempCollectionFactory();
 		Collection<Document> tempCollection = tempCollectionFactory.getCollection(name, Document.class);
 
 		if (entityByName == null) {