diff --git a/arangod/Cluster/AgencyComm.cpp b/arangod/Cluster/AgencyComm.cpp
index 0bfefe2a06..81b2bfef72 100644
--- a/arangod/Cluster/AgencyComm.cpp
+++ b/arangod/Cluster/AgencyComm.cpp
@@ -687,7 +687,7 @@ bool AgencyComm::addEndpoint (std::string const& endpointSpecification,
     while (it != _globalEndpoints.end()) {
       AgencyEndpoint const* agencyEndpoint = (*it);
 
-      TRI_ASSERT(agencyEndpoint != 0);
+      TRI_ASSERT(agencyEndpoint != nullptr);
 
       if (agencyEndpoint->_endpoint->getSpecification() == endpointSpecification) {
         // a duplicate. just ignore
@@ -701,7 +701,7 @@ bool AgencyComm::addEndpoint (std::string const& endpointSpecification,
     for (size_t i = 0; i < NumConnections; ++i) {
       AgencyEndpoint* agencyEndpoint = createAgencyEndpoint(endpointSpecification);
 
-      if (agencyEndpoint == 0) {
+      if (agencyEndpoint == nullptr) {
         return false;
       }
 
@@ -793,7 +793,7 @@ const std::vector<std::string> AgencyComm::getEndpoints () {
     while (it != AgencyComm::_globalEndpoints.end()) {
       AgencyEndpoint const* agencyEndpoint = (*it);
 
-      TRI_ASSERT(agencyEndpoint != 0);
+      TRI_ASSERT(agencyEndpoint != nullptr);
 
       result.push_back(agencyEndpoint->_endpoint->getSpecification());
       ++it;
@@ -823,7 +823,7 @@ const std::string AgencyComm::getEndpointsString () {
 
       AgencyEndpoint const* agencyEndpoint = (*it);
 
-      TRI_ASSERT(agencyEndpoint != 0);
+      TRI_ASSERT(agencyEndpoint != nullptr);
 
       result.append(agencyEndpoint->_endpoint->getSpecification());
       ++it;
@@ -893,9 +893,9 @@ std::string AgencyComm::generateStamp () {
 AgencyEndpoint* AgencyComm::createAgencyEndpoint (std::string const& endpointSpecification) {
   triagens::rest::Endpoint* endpoint = triagens::rest::Endpoint::clientFactory(endpointSpecification);
 
-  if (endpoint == 0) {
+  if (endpoint == nullptr) {
     // could not create endpoint...
-    return 0;
+    return nullptr;
   }
 
   triagens::httpclient::GeneralClientConnection* connection =
@@ -905,10 +905,10 @@ AgencyEndpoint* AgencyComm::createAgencyEndpoint (std::string const& endpointSpe
                                                            _globalConnectionOptions._connectRetries,
                                                            0);
 
-  if (connection == 0) {
+  if (connection == nullptr) {
     delete endpoint;
 
-    return 0;
+    return nullptr;
   }
 
   return new AgencyEndpoint(endpoint, connection);
@@ -926,7 +926,7 @@ AgencyCommResult AgencyComm::sendServerState (double ttl) {
   // construct JSON value { "status": "...", "time": "..." }
   TRI_json_t* json = TRI_CreateArrayJson(TRI_UNKNOWN_MEM_ZONE);
 
-  if (json == 0) {
+  if (json == nullptr) {
     return AgencyCommResult();
   }
 
@@ -979,7 +979,7 @@ bool AgencyComm::increaseVersion (std::string const& key) {
     // no version key found, now set it
     TRI_json_t* json = triagens::basics::JsonHelper::uint64String(TRI_UNKNOWN_MEM_ZONE, 1);
 
-    if (json == 0) {
+    if (json == nullptr) {
       return false;
     }
 
@@ -1008,13 +1008,13 @@ bool AgencyComm::increaseVersion (std::string const& key) {
   // version key found, now update it
   TRI_json_t* oldJson = triagens::basics::JsonHelper::uint64String(TRI_UNKNOWN_MEM_ZONE, version);
 
-  if (oldJson == 0) {
+  if (oldJson == nullptr) {
     return false;
   }
 
   TRI_json_t* newJson = triagens::basics::JsonHelper::uint64String(TRI_UNKNOWN_MEM_ZONE, version + 1);
 
-  if (newJson == 0) {
+  if (newJson == nullptr) {
     TRI_FreeJson(TRI_UNKNOWN_MEM_ZONE, oldJson);
     return false;
   }
@@ -1231,7 +1231,7 @@ bool AgencyComm::lockRead (std::string const& key,
                            double timeout) {
   TRI_json_t* json = TRI_CreateString2CopyJson(TRI_UNKNOWN_MEM_ZONE, "READ", 4);
 
-  if (json == 0) {
+  if (json == nullptr) {
     return false;
   }
 
@@ -1249,7 +1249,7 @@ bool AgencyComm::lockWrite (std::string const& key,
                             double timeout) {
   TRI_json_t* json = TRI_CreateString2CopyJson(TRI_UNKNOWN_MEM_ZONE, "WRITE", 5);
 
-  if (json == 0) {
+  if (json == nullptr) {
     return false;
   }
 
@@ -1266,7 +1266,7 @@ bool AgencyComm::unlockRead (std::string const& key,
                              double timeout) {
   TRI_json_t* json = TRI_CreateString2CopyJson(TRI_UNKNOWN_MEM_ZONE, "READ", 4);
 
-  if (json == 0) {
+  if (json == nullptr) {
     return false;
   }
 
@@ -1283,7 +1283,7 @@ bool AgencyComm::unlockWrite (std::string const& key,
                               double timeout) {
   TRI_json_t* json = TRI_CreateString2CopyJson(TRI_UNKNOWN_MEM_ZONE, "WRITE", 5);
 
-  if (json == 0) {
+  if (json == nullptr) {
     return false;
   }
 
@@ -1311,7 +1311,7 @@ AgencyCommResult AgencyComm::uniqid (std::string const& key,
     if (result.httpCode() == (int) triagens::rest::HttpResponse::NOT_FOUND) {
       TRI_json_t* json = TRI_CreateString2CopyJson(TRI_UNKNOWN_MEM_ZONE, "0", 1);
 
-      if (json != 0) {
+      if (json != nullptr) {
         // create the key on the fly
         setValue(key, json, 0.0);
         TRI_FreeJson(TRI_UNKNOWN_MEM_ZONE, json);
@@ -1327,20 +1327,20 @@ AgencyCommResult AgencyComm::uniqid (std::string const& key,
 
     result.parse("", false);
 
-    TRI_json_t* oldJson = 0;
+    TRI_json_t* oldJson = nullptr;
 
     std::map<std::string, AgencyCommResultEntry>::iterator it = result._values.begin();
 
     if (it != result._values.end()) {
       // steal the json
       oldJson = (*it).second._json;
-      (*it).second._json = 0;
+      (*it).second._json = nullptr;
     }
     else {
       oldJson = TRI_CreateString2CopyJson(TRI_UNKNOWN_MEM_ZONE, "0", 1);
     }
 
-    if (oldJson == 0) {
+    if (oldJson == nullptr) {
       return AgencyCommResult();
     }
 
@@ -1348,7 +1348,7 @@ AgencyCommResult AgencyComm::uniqid (std::string const& key,
     const uint64_t newValue = oldValue + count;
     TRI_json_t* newJson = triagens::basics::JsonHelper::uint64String(TRI_UNKNOWN_MEM_ZONE, newValue);
 
-    if (newJson == 0) {
+    if (newJson == nullptr) {
       TRI_FreeJson(TRI_UNKNOWN_MEM_ZONE, oldJson);
       return AgencyCommResult();
     }
@@ -1406,7 +1406,7 @@ bool AgencyComm::lock (std::string const& key,
   while (true) {
     TRI_json_t* oldJson = TRI_CreateString2CopyJson(TRI_UNKNOWN_MEM_ZONE, "UNLOCKED", 8);
 
-    if (oldJson == 0) {
+    if (oldJson == nullptr) {
       return false;
     }
 
@@ -1466,7 +1466,7 @@ bool AgencyComm::unlock (std::string const& key,
   while (true) {
     TRI_json_t* newJson = TRI_CreateString2CopyJson(TRI_UNKNOWN_MEM_ZONE, "UNLOCKED", 8);
 
-    if (newJson == 0) {
+    if (newJson == nullptr) {
       return false;
     }
 
@@ -1516,7 +1516,7 @@ AgencyEndpoint* AgencyComm::popEndpoint (std::string const& endpoint) {
       while (it != _globalEndpoints.end()) {
         AgencyEndpoint* agencyEndpoint = (*it);
 
-        TRI_ASSERT(agencyEndpoint != 0);
+        TRI_ASSERT(agencyEndpoint != nullptr);
 
         if (! endpoint.empty() &&
             agencyEndpoint->_endpoint->getSpecification() != endpoint) {
@@ -1556,7 +1556,7 @@ AgencyEndpoint* AgencyComm::popEndpoint (std::string const& endpoint) {
 
   // just to shut up compilers
   TRI_ASSERT(false);
-  return 0;
+  return nullptr;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -1568,7 +1568,7 @@ void AgencyComm::requeueEndpoint (AgencyEndpoint* agencyEndpoint,
   WRITE_LOCKER(AgencyComm::_globalLock);
   const size_t numEndpoints TRI_UNUSED = _globalEndpoints.size();
 
-  TRI_ASSERT(agencyEndpoint != 0);
+  TRI_ASSERT(agencyEndpoint != nullptr);
   TRI_ASSERT(agencyEndpoint->_busy);
 
   // set to non-busy
@@ -1633,7 +1633,7 @@ bool AgencyComm::sendWithFailover (triagens::rest::HttpRequest::HttpRequestType
   while (tries++ < numEndpoints) {
     AgencyEndpoint* agencyEndpoint = popEndpoint(forceEndpoint);
 
-    TRI_ASSERT(agencyEndpoint != 0);
+    TRI_ASSERT(agencyEndpoint != nullptr);
 
     send(agencyEndpoint->_connection,
          method,
@@ -1738,7 +1738,7 @@ bool AgencyComm::send (triagens::httpclient::GeneralClientConnection* connection
                        std::string const& url,
                        std::string const& body) {
 
-  TRI_ASSERT(connection != 0);
+  TRI_ASSERT(connection != nullptr);
 
   if (method == triagens::rest::HttpRequest::HTTP_REQUEST_GET ||
       method == triagens::rest::HttpRequest::HTTP_REQUEST_HEAD ||
@@ -1778,7 +1778,7 @@ bool AgencyComm::send (triagens::httpclient::GeneralClientConnection* connection
                                                                     body.size(),
                                                                     headers);
 
-  if (response == 0) {
+  if (response == nullptr) {
     result._message = "could not send request to agency";
     LOG_TRACE("sending request to agency failed");
 
diff --git a/arangod/Cluster/ClusterComm.cpp b/arangod/Cluster/ClusterComm.cpp
index 77d2a5f21c..678d196f12 100644
--- a/arangod/Cluster/ClusterComm.cpp
+++ b/arangod/Cluster/ClusterComm.cpp
@@ -546,7 +546,7 @@ ClusterCommResult* ClusterComm::wait (
         }
       }
       // If we found nothing, we have to look through the send queue:
-      if (!found) {
+      if (! found) {
         basics::ConditionLocker sendlocker(&somethingToSend);
         for (q = toSend.begin(); q != toSend.end(); q++) {
           op = *q;
@@ -556,7 +556,7 @@ ClusterCommResult* ClusterComm::wait (
           }
         }
       }
-      if (!found) {
+      if (! found) {
         // Nothing known about this operation, return with failure:
         res = new ClusterCommResult();
         res->clientTransactionID = clientTransactionID;
diff --git a/arangod/Cluster/ClusterInfo.cpp b/arangod/Cluster/ClusterInfo.cpp
index 5feb98683d..047a856a27 100644
--- a/arangod/Cluster/ClusterInfo.cpp
+++ b/arangod/Cluster/ClusterInfo.cpp
@@ -106,7 +106,7 @@ static string extractErrorMessage (string const& shardId,
 ////////////////////////////////////////////////////////////////////////////////
 
 CollectionInfo::CollectionInfo ()
-  : _json(0) {
+  : _json(nullptr) {
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -124,7 +124,7 @@ CollectionInfo::CollectionInfo (TRI_json_t* json)
 CollectionInfo::CollectionInfo (CollectionInfo const& other) :
   _json(other._json) {
 
-  if (other._json != 0) {
+  if (other._json != nullptr) {
     _json = TRI_CopyJson(TRI_UNKNOWN_MEM_ZONE, other._json);
   }
 }
@@ -134,11 +134,11 @@ CollectionInfo::CollectionInfo (CollectionInfo const& other) :
 ////////////////////////////////////////////////////////////////////////////////
 
 CollectionInfo& CollectionInfo::operator= (CollectionInfo const& other) {
-  if (other._json != 0 && this != &other) {
+  if (other._json != nullptr && this != &other) {
     _json = TRI_CopyJson(TRI_UNKNOWN_MEM_ZONE, other._json);
   }
   else {
-    _json = 0;
+    _json = nullptr;
   }
 
   return *this;
@@ -149,7 +149,7 @@ CollectionInfo& CollectionInfo::operator= (CollectionInfo const& other) {
 ////////////////////////////////////////////////////////////////////////////////
 
 CollectionInfo::~CollectionInfo () {
-  if (_json != 0) {
+  if (_json != nullptr) {
     TRI_FreeJson(TRI_UNKNOWN_MEM_ZONE, _json);
   }
 }
@@ -215,7 +215,7 @@ CollectionInfoCurrent::~CollectionInfoCurrent () {
 void CollectionInfoCurrent::freeAllJsons () {
   map<ShardID, TRI_json_t*>::iterator it;
   for (it = _jsons.begin(); it != _jsons.end(); ++it) {
-    if (it->second != 0) {
+    if (it->second != nullptr) {
       TRI_FreeJson(TRI_UNKNOWN_MEM_ZONE, it->second);
     }
   }
@@ -228,7 +228,7 @@ void CollectionInfoCurrent::freeAllJsons () {
 void CollectionInfoCurrent::copyAllJsons () {
   map<ShardID, TRI_json_t*>::iterator it;
   for (it = _jsons.begin(); it != _jsons.end(); ++it) {
-    if (0 != it->second) {
+    if (nullptr != it->second) {
       it->second = TRI_CopyJson(TRI_UNKNOWN_MEM_ZONE, it->second);
     }
   }
@@ -435,7 +435,7 @@ void ClusterInfo::clearPlannedDatabases () {
   while (it != _plannedDatabases.end()) {
     TRI_json_t* json = (*it).second;
 
-    if (json != 0) {
+    if (json != nullptr) {
       TRI_FreeJson(TRI_UNKNOWN_MEM_ZONE, json);
     }
     ++it;
@@ -457,7 +457,7 @@ void ClusterInfo::clearCurrentDatabases () {
     while (it2 != (*it).second.end()) {
       TRI_json_t* json = (*it2).second;
 
-      if (json != 0) {
+      if (json != nullptr) {
         TRI_FreeJson(TRI_UNKNOWN_MEM_ZONE, json);
       }
 
@@ -500,7 +500,7 @@ void ClusterInfo::loadPlannedDatabases () {
       TRI_json_t* options = (*it).second._json;
 
       // steal the json
-      (*it).second._json = 0;
+      (*it).second._json = nullptr;
       _plannedDatabases.insert(std::make_pair(name, options));
 
       ++it;
@@ -562,7 +562,7 @@ void ClusterInfo::loadCurrentDatabases () {
         // got a server name
         TRI_json_t* json = (*it).second._json;
         // steal the JSON
-        (*it).second._json = 0;
+        (*it).second._json = nullptr;
         (*it2).second.insert(std::make_pair(parts[1], json));
       }
 
@@ -941,7 +941,7 @@ int ClusterInfo::createDatabaseCoordinator (string const& name,
     }
 
     res = ac.casValue("Plan/Databases/"+name, json, false, 0.0, realTimeout);
-    if (!res.successful()) {
+    if (! res.successful()) {
       if (res._statusCode == triagens::rest::HttpResponse::PRECONDITION_FAILED) {
         return setErrormsg(TRI_ERROR_ARANGO_DUPLICATE_NAME, errorMsg);
       }
@@ -953,7 +953,7 @@ int ClusterInfo::createDatabaseCoordinator (string const& name,
 
   // Now wait for it to appear and be complete:
   res = ac.getValues("Current/Version", false);
-  if (!res.successful()) {
+  if (! res.successful()) {
     return setErrormsg(TRI_ERROR_CLUSTER_COULD_NOT_READ_CURRENT_VERSION,
                        errorMsg);
   }
@@ -1233,7 +1233,7 @@ int ClusterInfo::dropCollectionCoordinator (string const& databaseName,
 
     res = ac.removeValues("Plan/Collections/"+databaseName+"/"+collectionID,
                           false);
-    if (!res.successful()) {
+    if (! res.successful()) {
       if (res._statusCode == rest::HttpResponse::NOT_FOUND) {
         return setErrormsg(TRI_ERROR_ARANGO_COLLECTION_NOT_FOUND, errorMsg);
       }
@@ -1844,7 +1844,7 @@ void ClusterInfo::loadServers () {
       TRI_json_t const* sub
         = triagens::basics::JsonHelper::getArrayElement((*it).second._json,
                                                         "endpoint");
-      if (0 != sub) {
+      if (nullptr != sub) {
         const std::string server = triagens::basics::JsonHelper::getStringValue(sub, "");
 
         _servers.emplace(std::make_pair((*it).first, server));