diff --git a/arangod/Aql/RestAqlHandler.cpp b/arangod/Aql/RestAqlHandler.cpp
index 886b87e4b3..c9a4f4812e 100644
--- a/arangod/Aql/RestAqlHandler.cpp
+++ b/arangod/Aql/RestAqlHandler.cpp
@@ -119,19 +119,13 @@ void RestAqlHandler::createQueryFromJson () {
   Json plan;
   Json options;
 
-  try {
-    plan = queryJson.get("plan").copy();
-  }
-  catch (...) {
+  plan = queryJson.get("plan").copy();   // cannot throw
+  if (plan.isEmpty()) {
     generateError(HttpResponse::BAD, TRI_ERROR_INTERNAL,
       "body must be an object with attribute \"plan\"");
     return;
   }
-  try {
-    options = queryJson.get("options").copy();
-  }
-  catch (...) {
-  }
+  options = queryJson.get("options").copy();
 
   auto query = new Query(vocbase, plan, options.steal());
   QueryResult res = query->prepare();
@@ -193,6 +187,33 @@ void RestAqlHandler::parseQuery () {
 ////////////////////////////////////////////////////////////////////////////////
 
 void RestAqlHandler::explainQuery () {
+  Json queryJson(TRI_UNKNOWN_MEM_ZONE, parseJsonBody());
+  if (queryJson.isEmpty()) {
+    return;
+  }
+  
+  TRI_vocbase_t* vocbase = GetContextVocBase();
+  if (vocbase == nullptr) {
+    generateError(HttpResponse::BAD,
+                  TRI_ERROR_INTERNAL, "cannot get vocbase from context");
+    return;
+  }
+
+  Json queryString;
+  Json parameters;
+  Json options;
+
+  queryString = queryJson.get("plan").copy();       // cannot throw
+  if (queryString.isEmpty()) {
+    generateError(HttpResponse::BAD, TRI_ERROR_INTERNAL,
+      "body must be an object with attribute \"plan\"");
+    return;
+  }
+  parameters = queryJson.get("parameters").copy();  // cannot throw
+  options = queryJson.get("options").copy();        // cannot throw
+
+  // ...
+
   _response = createResponse(triagens::rest::HttpResponse::OK);
   _response->setContentType("application/json; charset=utf-8");
   Json answerBody(Json::Array, 1);
diff --git a/arangod/RestServer/ArangoServer.cpp b/arangod/RestServer/ArangoServer.cpp
index 2d42bf16c8..7a3e7f3da5 100644
--- a/arangod/RestServer/ArangoServer.cpp
+++ b/arangod/RestServer/ArangoServer.cpp
@@ -846,6 +846,7 @@ int ArangoServer::startupServer () {
   _pairForAql = new std::pair<ApplicationV8*, aql::QueryRegistry*>;
   _pairForAql->first = _applicationV8;
   _pairForAql->second = _queryRegistry;
+  _server->_queryRegistry = static_cast<void*>(_queryRegistry);
 
   // ...........................................................................
   // create endpoints and handlers
@@ -915,6 +916,8 @@ int ArangoServer::startupServer () {
 
   _applicationServer->stop();
 
+  _server->_queryRegistry = nullptr;
+
   delete _queryRegistry;
   _queryRegistry = nullptr;
   delete _pairForAql;
diff --git a/arangod/VocBase/server.cpp b/arangod/VocBase/server.cpp
index 5b14d14767..3a581e941d 100644
--- a/arangod/VocBase/server.cpp
+++ b/arangod/VocBase/server.cpp
@@ -35,6 +35,7 @@
 
 #include <regex.h>
 
+#include "Aql/QueryRegistry.h"
 #include "Basics/conversions.h"
 #include "Basics/files.h"
 #include "Basics/hashes.h"
@@ -1493,6 +1494,12 @@ static void DatabaseManager (void* data) {
       }
 
       usleep(DATABASE_MANAGER_INTERVAL);
+      // The following is only necessary after a wait:
+      auto queryRegistry = static_cast<triagens::aql::QueryRegistry*>
+                                      (server->_queryRegistry);
+      if (queryRegistry != nullptr) {
+        queryRegistry->expireQueries();
+      }
     }
 
     // next iteration
@@ -1626,6 +1633,8 @@ int TRI_InitServer (TRI_server_t* server,
 
   server->_disableReplicationAppliers = disableAppliers;
 
+  server->_queryRegistry = nullptr;   // will be filled in later
+
   server->_initialised = true;
 
   return TRI_ERROR_NO_ERROR;
diff --git a/arangod/VocBase/server.h b/arangod/VocBase/server.h
index 512aa136ca..f3aa0db507 100644
--- a/arangod/VocBase/server.h
+++ b/arangod/VocBase/server.h
@@ -74,6 +74,7 @@ typedef struct TRI_server_s {
   bool                        _hasCreatedSystemDatabase;
 
   bool                        _initialised;
+  void*                       _queryRegistry;
 }
 TRI_server_t;