diff --git a/api/src/main/java/com/rbmhtechnology/vind/api/Document.java b/api/src/main/java/com/rbmhtechnology/vind/api/Document.java
index 7b3ba4f3..b181773e 100644
--- a/api/src/main/java/com/rbmhtechnology/vind/api/Document.java
+++ b/api/src/main/java/com/rbmhtechnology/vind/api/Document.java
@@ -13,6 +13,10 @@
  */
 public interface Document {
 
+    long VERSION_MUST_EXIST = 1;
+    long VERSION_DONT_CARE = 0;
+    long VERSION_MUST_NOT_EXIST = -1;
+
     /**
      * Sets a value in a document field. If the field had already a value it is overwritten by the new value.
      * @param field Name of the field to set.
@@ -301,6 +305,12 @@ public interface Document {
      */
     String getType();
 
+    /**
+     * Gets the document version. This field is used for optimistic concurrency.
+     * @return document version
+     */
+    long getVersion();
+
     /**
      * Gets the document distance.
      * @return a distance for the document.
diff --git a/api/src/main/java/com/rbmhtechnology/vind/model/DocumentFactory.java b/api/src/main/java/com/rbmhtechnology/vind/model/DocumentFactory.java
index cfcdf5c3..e6ead58e 100644
--- a/api/src/main/java/com/rbmhtechnology/vind/model/DocumentFactory.java
+++ b/api/src/main/java/com/rbmhtechnology/vind/model/DocumentFactory.java
@@ -83,7 +83,33 @@ public Map<String, FieldDescriptor<?>> getFields() {
      * @return A {@link Document} with the configured {@link FieldDescriptor}.
      */
     public Document createDoc(String id) {
-        return new DocumentImpl(id, this.type);
+        return createDoc(id, Document.VERSION_DONT_CARE);
+    }
+
+    /**
+     * Creates an instance of a {@link Document} within the schema of the actual configuration of the factory.
+     * If a document with the same {@code id} already exists, indexing this document will fail.
+     * @param id Identification string of the new document.
+     * @return A {@link Document} with the configured {@link FieldDescriptor}.
+     */
+    public Document createNewDoc(String id) {
+        return createDoc(id, Document.VERSION_MUST_NOT_EXIST);
+    }
+
+    /**
+     * Creates an instance of a {@link Document} within the schema of the actual configuration of the factory with
+     * the provided document-version.
+     *
+     * @param id Identification string of the new document.
+     * @param docVersion the document version, or one of the pre-defined constants.
+     * @return A {@link Document} with the configured {@link FieldDescriptor}.
+     *
+     * @see Document#VERSION_DONT_CARE
+     * @see Document#VERSION_MUST_NOT_EXIST
+     * @see Document#VERSION_MUST_EXIST
+     */
+    public Document createDoc(String id, long docVersion) {
+        return new DocumentImpl(id, this.type, docVersion);
     }
 
     /**
@@ -128,14 +154,16 @@ class DocumentImpl implements Document {
         private final Set<Document> children = new HashSet<>();
         private final String id;
         private final String type;
+        private final long version;
         private float score;
         private float distance;
         private Integer childCount;
 
-        private DocumentImpl(String id, String type) {
+        private DocumentImpl(String id, String type, long version) {
             //this.values.put(DocumentFactory.ID, id);
             this.id = id;
             this.type = type;
+            this.version = version;
         }
 
         /**
@@ -660,6 +688,14 @@ public String getType() {
             return type;
         }
 
+        /**
+         * {@inheritDoc}
+         */
+        @Override
+        public long getVersion() {
+            return version;
+        }
+
         /**
          * {@inheritDoc}
          */
diff --git a/backend/solr/src/main/java/com/rbmhtechnology/vind/solr/backend/SolrSearchServer.java b/backend/solr/src/main/java/com/rbmhtechnology/vind/solr/backend/SolrSearchServer.java
index 53ae2901..01f25058 100644
--- a/backend/solr/src/main/java/com/rbmhtechnology/vind/solr/backend/SolrSearchServer.java
+++ b/backend/solr/src/main/java/com/rbmhtechnology/vind/solr/backend/SolrSearchServer.java
@@ -290,6 +290,7 @@ private SolrInputDocument createInputDocument(Document doc) {
 
         document.addField(ID, doc.getId());
         document.addField(TYPE, doc.getType());
+        document.addField(VERSION, doc.getVersion());
 
         return document;
     }
diff --git a/backend/solr/src/main/java/com/rbmhtechnology/vind/solr/backend/SolrUtils.java b/backend/solr/src/main/java/com/rbmhtechnology/vind/solr/backend/SolrUtils.java
index 76081a04..4b85f2a6 100644
--- a/backend/solr/src/main/java/com/rbmhtechnology/vind/solr/backend/SolrUtils.java
+++ b/backend/solr/src/main/java/com/rbmhtechnology/vind/solr/backend/SolrUtils.java
@@ -756,6 +756,7 @@ public static Type getFromClass(Class clazz) {
 
         public static final String ID = "_id_";
         public static final String TYPE = "_type_";
+        public static final String VERSION = "_version_";
         public static final String SCORE = "score";
         public static final String DISTANCE = "_distance_";
         public static final String TEXT = "text";
@@ -905,7 +906,9 @@ public static List<Document> buildResultList(SolrDocumentList results, Map<Strin
 
             return results.stream().map(result -> {
 
-                Document document = factory.createDoc((String) result.getFieldValue(Fieldname.ID));
+                final Document document = factory.createDoc((
+                        String) result.getFieldValue(Fieldname.ID),
+                        (long) result.getFieldValue(Fieldname.VERSION));
 
                 if (childCounts != null) {
                     document.setChildCount(ObjectUtils.defaultIfNull(childCounts.get(document.getId()), 0));
@@ -922,6 +925,7 @@ public static List<Document> buildResultList(SolrDocumentList results, Map<Strin
                 result.getFieldNames().stream()
                         .filter(name -> !name.equals(Fieldname.ID))
                         .filter(name -> !name.equals(Fieldname.TYPE))
+                        .filter(name -> !name.equals(Fieldname.VERSION))
                         .filter(name -> !name.equals(Fieldname.SCORE))
                         .filter(name -> !name.equals(Fieldname.DISTANCE))
                         .forEach(name -> {