diff --git a/src/main/java/de/pzzz/vertx/RestDataAccess.java b/src/main/java/de/pzzz/vertx/RestDataAccess.java
index e93e0b7..4b51a4c 100644
--- a/src/main/java/de/pzzz/vertx/RestDataAccess.java
+++ b/src/main/java/de/pzzz/vertx/RestDataAccess.java
@@ -2,9 +2,9 @@ package de.pzzz.vertx;
 
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.HashMap;
 import java.util.Map;
 import java.util.UUID;
+import java.util.concurrent.ConcurrentHashMap;
 
 import io.vertx.core.Vertx;
 import io.vertx.core.eventbus.Message;
@@ -14,7 +14,7 @@ import io.vertx.ext.web.Router;
 import io.vertx.ext.web.RoutingContext;
 
 public class RestDataAccess<T extends SerializableWithId> {
-    private Map<String, T> dataMap = new HashMap<>();
+    private Map<String, T> dataMap = new ConcurrentHashMap<>();
     protected final Class<T> classReference;
 
     public RestDataAccess(final Class<T> classReference) {