diff --git a/arangod/Aql/QueryList.cpp b/arangod/Aql/QueryList.cpp
index e32e2d7a40..c4af566fa1 100644
--- a/arangod/Aql/QueryList.cpp
+++ b/arangod/Aql/QueryList.cpp
@@ -29,6 +29,7 @@
 
 #include "Aql/QueryList.h"
 #include "Aql/Query.h"
+#include "Basics/logging.h"
 #include "Basics/ReadLocker.h"
 #include "Basics/WriteLocker.h"
 #include "VocBase/vocbase.h"
@@ -216,15 +217,21 @@ void QueryList::remove (Query const* query,
 ////////////////////////////////////////////////////////////////////////////////
 
 int QueryList::kill (TRI_voc_tick_t id) {
-  WRITE_LOCKER(_lock);
+  {
+    WRITE_LOCKER(_lock);
   
-  auto it = _current.find(id);
+    auto it = _current.find(id);
 
-  if (it == _current.end()) {
-    return TRI_ERROR_QUERY_NOT_FOUND;
+    if (it == _current.end()) {
+      return TRI_ERROR_QUERY_NOT_FOUND;
+    }
+
+    const_cast<triagens::aql::Query*>((*it).second->query)->killed(true);
   }
+  
+  // log outside the lock  
+  LOG_WARNING("killing AQL query '%llu'", (unsigned long long) id);
 
-  const_cast<triagens::aql::Query*>((*it).second->query)->killed(true);
   return TRI_ERROR_NO_ERROR;
 }
 
diff --git a/arangod/Aql/QueryList.h b/arangod/Aql/QueryList.h
index 0f6b9d00b8..870d43901b 100644
--- a/arangod/Aql/QueryList.h
+++ b/arangod/Aql/QueryList.h
@@ -101,6 +101,8 @@ namespace triagens {
 
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief whether or not queries are tracked
+/// we're not using a lock here for performance reasons - thus concurrent 
+/// modifications of this variable are possible but are considered unharmful
 ////////////////////////////////////////////////////////////////////////////////
 
         inline bool enabled () const {
@@ -109,6 +111,8 @@ namespace triagens {
 
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief toggle query tracking
+/// we're not using a lock here for performance reasons - thus concurrent 
+/// modifications of this variable are possible but are considered unharmful
 ////////////////////////////////////////////////////////////////////////////////
         
         inline void enabled (bool value) {
@@ -117,6 +121,8 @@ namespace triagens {
 
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief whether or not slow queries are tracked
+/// we're not using a lock here for performance reasons - thus concurrent 
+/// modifications of this variable are possible but are considered unharmful
 ////////////////////////////////////////////////////////////////////////////////
 
         inline bool trackSlowQueries () const {
@@ -125,6 +131,8 @@ namespace triagens {
 
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief toggle slow query tracking
+/// we're not using a lock here for performance reasons - thus concurrent 
+/// modifications of this variable are possible but are considered unharmful
 ////////////////////////////////////////////////////////////////////////////////
         
         inline void trackSlowQueries (bool value) {
@@ -133,6 +141,8 @@ namespace triagens {
 
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief threshold for slow queries (in seconds)
+/// we're not using a lock here for performance reasons - thus concurrent 
+/// modifications of this variable are possible but are considered unharmful
 ////////////////////////////////////////////////////////////////////////////////
 
         inline double slowQueryThreshold () const {
@@ -141,6 +151,8 @@ namespace triagens {
 
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief set the slow query threshold
+/// we're not using a lock here for performance reasons - thus concurrent 
+/// modifications of this variable are possible but are considered unharmful
 ////////////////////////////////////////////////////////////////////////////////
         
         inline void slowQueryThreshold (double value) {
@@ -153,6 +165,8 @@ namespace triagens {
 
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief return the max number of slow queries to keep
+/// we're not using a lock here for performance reasons - thus concurrent 
+/// modifications of this variable are possible but are considered unharmful
 ////////////////////////////////////////////////////////////////////////////////
 
         inline size_t maxSlowQueries () const {
@@ -161,6 +175,8 @@ namespace triagens {
 
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief set the max number of slow queries to keep
+/// we're not using a lock here for performance reasons - thus concurrent 
+/// modifications of this variable are possible but are considered unharmful
 ////////////////////////////////////////////////////////////////////////////////
 
         inline void maxSlowQueries (size_t value) {
@@ -173,6 +189,8 @@ namespace triagens {
 
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief return the max length of query strings that are stored / returned
+/// we're not using a lock here for performance reasons - thus concurrent 
+/// modifications of this variable are possible but are considered unharmful
 ////////////////////////////////////////////////////////////////////////////////
 
         inline size_t maxQueryStringLength () const {
@@ -181,6 +199,8 @@ namespace triagens {
 
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief set the max length of query strings that are stored / returned
+/// we're not using a lock here for performance reasons - thus concurrent 
+/// modifications of this variable are possible but are considered unharmful
 ////////////////////////////////////////////////////////////////////////////////
         
         inline void maxQueryStringLength (size_t value) {