diff --git a/arangod/RocksDBEngine/RocksDBEngine.cpp b/arangod/RocksDBEngine/RocksDBEngine.cpp
index a2c669d7bf..ddfdf69300 100644
--- a/arangod/RocksDBEngine/RocksDBEngine.cpp
+++ b/arangod/RocksDBEngine/RocksDBEngine.cpp
@@ -243,8 +243,8 @@ TransactionState* RocksDBEngine::createTransactionState(
 
 TransactionCollection* RocksDBEngine::createTransactionCollection(
     TransactionState* state, TRI_voc_cid_t cid, AccessMode::Type accessType,
-    int /*nestingLevel*/) {
-  return new RocksDBTransactionCollection(state, cid, accessType);
+    int nestingLevel) {
+  return new RocksDBTransactionCollection(state, cid, accessType, nestingLevel);
 }
 
 void RocksDBEngine::addParametersForNewCollection(VPackBuilder& builder,
diff --git a/arangod/RocksDBEngine/RocksDBTransactionCollection.cpp b/arangod/RocksDBEngine/RocksDBTransactionCollection.cpp
index 043b8e469f..3b8dea4380 100644
--- a/arangod/RocksDBEngine/RocksDBTransactionCollection.cpp
+++ b/arangod/RocksDBEngine/RocksDBTransactionCollection.cpp
@@ -35,9 +35,11 @@
 using namespace arangodb;
 
 RocksDBTransactionCollection::RocksDBTransactionCollection(
-    TransactionState* trx, TRI_voc_cid_t cid, AccessMode::Type accessType)
+    TransactionState* trx, TRI_voc_cid_t cid, AccessMode::Type accessType, int nestingLevel)
     : TransactionCollection(trx, cid),
       _accessType(accessType),
+      _lockType(AccessMode::Type::NONE),
+      _nestingLevel(nestingLevel),
       _initialNumberDocuments(0),
       _revision(0),
       _operationSize(0),
@@ -48,33 +50,43 @@ RocksDBTransactionCollection::RocksDBTransactionCollection(
 RocksDBTransactionCollection::~RocksDBTransactionCollection() {}
 
 /// @brief request a main-level lock for a collection
-int RocksDBTransactionCollection::lock() { return TRI_ERROR_NO_ERROR; }
+int RocksDBTransactionCollection::lock() { return lock(_accessType, 0); }
 
 /// @brief request a lock for a collection
 int RocksDBTransactionCollection::lock(AccessMode::Type accessType,
-                                       int /*nestingLevel*/) {
+                                       int nestingLevel) {
   if (isWrite(accessType) && !isWrite(_accessType)) {
     // wrong lock type
     return TRI_ERROR_INTERNAL;
   }
 
-  return TRI_ERROR_NO_ERROR;
+  if (isLocked()) {
+    // already locked
+    return TRI_ERROR_NO_ERROR;
+  }
+
+  return doLock(accessType, nestingLevel);
 }
 
 /// @brief request an unlock for a collection
 int RocksDBTransactionCollection::unlock(AccessMode::Type accessType,
-                                         int /*nestingLevel*/) {
+                                         int nestingLevel) {
   if (isWrite(accessType) && !isWrite(_accessType)) {
     // wrong lock type: write-unlock requested but collection is read-only
     return TRI_ERROR_INTERNAL;
   }
 
-  return TRI_ERROR_NO_ERROR;
+  if (!isLocked()) {
+    // already unlocked
+    return TRI_ERROR_NO_ERROR;
+  }
+
+  return doUnlock(accessType, nestingLevel);
 }
 
 /// @brief check if a collection is locked in a specific mode in a transaction
 bool RocksDBTransactionCollection::isLocked(AccessMode::Type accessType,
-                                            int /*nestingLevel*/) const {
+                                            int nestingLevel) const {
   if (isWrite(accessType) && !isWrite(_accessType)) {
     // wrong lock type
     LOG_TOPIC(WARN, arangodb::Logger::FIXME)
@@ -82,14 +94,12 @@ bool RocksDBTransactionCollection::isLocked(AccessMode::Type accessType,
     return false;
   }
 
-  // TODO
-  return false;
+  return isLocked();
 }
 
 /// @brief check whether a collection is locked at all
 bool RocksDBTransactionCollection::isLocked() const {
-  // TODO
-  return false;
+  return (_lockType != AccessMode::Type::NONE);
 }
 
 /// @brief whether or not any write operations for the collection happened
@@ -127,12 +137,21 @@ int RocksDBTransactionCollection::updateUsage(AccessMode::Type accessType,
     // upgrade collection type to write-access
     _accessType = accessType;
   }
+  
+  if (nestingLevel < _nestingLevel) {
+    _nestingLevel = nestingLevel;
+  }
 
   // all correct
   return TRI_ERROR_NO_ERROR;
 }
 
 int RocksDBTransactionCollection::use(int nestingLevel) {
+  if (_nestingLevel != nestingLevel) {
+    // only process our own collections
+    return TRI_ERROR_NO_ERROR;
+  }
+
   if (_collection == nullptr) {
     TRI_vocbase_col_status_e status;
     LOG_TRX(_transaction, nestingLevel) << "using collection " << _cid;
@@ -159,12 +178,29 @@ int RocksDBTransactionCollection::use(int nestingLevel) {
         static_cast<RocksDBCollection*>(_collection->getPhysical())->revision();
   }
 
+  if (isExclusive(_accessType) && !isLocked()) {
+    // r/w lock the collection
+    int res = doLock(_accessType, nestingLevel);
+
+    if (res != TRI_ERROR_NO_ERROR) {
+      return res;
+    }
+  }
+  
   return TRI_ERROR_NO_ERROR;
 }
 
-void RocksDBTransactionCollection::unuse(int /*nestingLevel*/) {}
+void RocksDBTransactionCollection::unuse(int nestingLevel) {
+  // nothing to do here. we're postponing the unlocking until release()
+}
 
 void RocksDBTransactionCollection::release() {
+  if (isLocked()) {
+    // unlock our own r/w locks
+    doUnlock(_accessType, 0);
+    _lockType = AccessMode::Type::NONE;
+  }
+  
   // the top level transaction releases all collections
   if (_collection != nullptr) {
     // unuse collection, remove usage-lock
@@ -206,3 +242,99 @@ void RocksDBTransactionCollection::addOperation(
   }
   _operationSize += operationSize;
 }
+
+/// @brief lock a collection
+int RocksDBTransactionCollection::doLock(AccessMode::Type type, int nestingLevel) {
+  if (!isExclusive(type)) {
+    return TRI_ERROR_NO_ERROR;
+  }
+  
+  TRI_ASSERT(_collection != nullptr);
+
+  if (CollectionLockState::_noLockHeaders != nullptr) {
+    std::string collName(_collection->name());
+    auto it = CollectionLockState::_noLockHeaders->find(collName);
+    if (it != CollectionLockState::_noLockHeaders->end()) {
+      // do not lock by command
+      // LOCKING-DEBUG
+      // std::cout << "LockCollection blocked: " << collName << std::endl;
+      return TRI_ERROR_NO_ERROR;
+    }
+  }
+
+  TRI_ASSERT(!isLocked());
+
+  LogicalCollection* collection = _collection;
+  TRI_ASSERT(collection != nullptr);
+
+  auto physical = static_cast<RocksDBCollection*>(collection->getPhysical());
+  TRI_ASSERT(physical != nullptr);
+
+  double timeout = _transaction->timeout();
+  if (_transaction->hasHint(transaction::Hints::Hint::TRY_LOCK)) {
+    // give up early if we cannot acquire the lock instantly
+    timeout = 0.00000001;
+  }
+  
+  bool const useDeadlockDetector = !_transaction->hasHint(transaction::Hints::Hint::SINGLE_OPERATION);
+
+  LOG_TRX(_transaction, nestingLevel) << "write-locking collection " << _cid;
+  int res = physical->beginWriteTimed(useDeadlockDetector, timeout);
+
+  if (res == TRI_ERROR_NO_ERROR) {
+    _lockType = type;
+  } else if (res == TRI_ERROR_LOCK_TIMEOUT && timeout >= 0.1) {
+    LOG_TOPIC(WARN, Logger::QUERIES) << "timed out after " << timeout << " s waiting for " << AccessMode::typeString(type) << "-lock on collection '" << _collection->name() << "'";
+  } else if (res == TRI_ERROR_DEADLOCK) {
+    LOG_TOPIC(WARN, Logger::QUERIES) << "deadlock detected while trying to acquire " << AccessMode::typeString(type) << "-lock on collection '" << _collection->name() << "'";
+  }
+  
+  return res;
+}
+
+/// @brief unlock a collection
+int RocksDBTransactionCollection::doUnlock(AccessMode::Type type, int nestingLevel) {
+  if (!isExclusive(type) || !isExclusive(_lockType)) {
+    return TRI_ERROR_NO_ERROR;
+  }
+
+  if (_transaction->hasHint(transaction::Hints::Hint::LOCK_NEVER)) {
+    // never unlock
+    return TRI_ERROR_NO_ERROR;
+  }
+
+  TRI_ASSERT(_collection != nullptr);
+
+  if (CollectionLockState::_noLockHeaders != nullptr) {
+    std::string collName(_collection->name());
+    auto it = CollectionLockState::_noLockHeaders->find(collName);
+    if (it != CollectionLockState::_noLockHeaders->end()) {
+      // do not lock by command
+      // LOCKING-DEBUG
+      // std::cout << "UnlockCollection blocked: " << collName << std::endl;
+      return TRI_ERROR_NO_ERROR;
+    }
+  }
+
+  TRI_ASSERT(isLocked());
+
+  if (_nestingLevel < nestingLevel) {
+    // only process our own collections
+    return TRI_ERROR_NO_ERROR;
+  }
+
+  bool const useDeadlockDetector = !_transaction->hasHint(transaction::Hints::Hint::SINGLE_OPERATION);
+
+  LogicalCollection* collection = _collection;
+  TRI_ASSERT(collection != nullptr);
+
+  auto physical = static_cast<RocksDBCollection*>(collection->getPhysical());
+  TRI_ASSERT(physical != nullptr);
+
+  LOG_TRX(_transaction, nestingLevel) << "write-unlocking collection " << _cid;
+  physical->endWrite(useDeadlockDetector);
+
+  _lockType = AccessMode::Type::NONE;
+
+  return TRI_ERROR_NO_ERROR;
+}
diff --git a/arangod/RocksDBEngine/RocksDBTransactionCollection.h b/arangod/RocksDBEngine/RocksDBTransactionCollection.h
index 08cc3c3c0a..6bb3805864 100644
--- a/arangod/RocksDBEngine/RocksDBTransactionCollection.h
+++ b/arangod/RocksDBEngine/RocksDBTransactionCollection.h
@@ -40,7 +40,7 @@ class TransactionState;
 class RocksDBTransactionCollection final : public TransactionCollection {
  public:
 
-  RocksDBTransactionCollection(TransactionState* trx, TRI_voc_cid_t cid, AccessMode::Type accessType);
+  RocksDBTransactionCollection(TransactionState* trx, TRI_voc_cid_t cid, AccessMode::Type accessType, int nestingLevel);
   ~RocksDBTransactionCollection();
 
   /// @brief request a main-level lock for a collection
@@ -78,9 +78,18 @@ class RocksDBTransactionCollection final : public TransactionCollection {
   /// @brief add an operation for a transaction collection
   void addOperation(TRI_voc_document_operation_e operationType, uint64_t operationSize, TRI_voc_rid_t revisionId) ;
   void resetCounts();
+ 
+ private:
+  /// @brief request a lock for a collection
+  int doLock(AccessMode::Type, int nestingLevel);
+
+  /// @brief request an unlock for a collection
+  int doUnlock(AccessMode::Type, int nestingLevel);
 
  private:
   AccessMode::Type _accessType;  // access type (read|write)
+  AccessMode::Type _lockType;  // collection lock type, used for exclusive locks
+  int _nestingLevel;  // the transaction level that added this collection
   uint64_t _initialNumberDocuments;
   TRI_voc_rid_t _revision;
   uint64_t _operationSize;
diff --git a/arangod/RocksDBEngine/RocksDBTransactionState.cpp b/arangod/RocksDBEngine/RocksDBTransactionState.cpp
index 89c9a56730..7f846d3d68 100644
--- a/arangod/RocksDBEngine/RocksDBTransactionState.cpp
+++ b/arangod/RocksDBEngine/RocksDBTransactionState.cpp
@@ -103,9 +103,27 @@ RocksDBTransactionState::~RocksDBTransactionState() {
 Result RocksDBTransactionState::beginTransaction(transaction::Hints hints) {
   LOG_TRX(this, _nestingLevel) << "beginning " << AccessMode::typeString(_type)
                                << " transaction";
-  if (_nestingLevel == 0) {
-    TRI_ASSERT(_status == transaction::Status::CREATED);
+  
+  Result result = useCollections(_nestingLevel);
 
+  if (result.ok()) {
+    // all valid
+    if (_nestingLevel == 0) {
+      updateStatus(transaction::Status::RUNNING);
+    }
+  } else {
+    // something is wrong
+    if (_nestingLevel == 0) {
+      updateStatus(transaction::Status::ABORTED);
+    }
+
+    // free what we have got so far
+    unuseCollections(_nestingLevel);
+
+    return result;
+  }
+
+  if (_nestingLevel == 0) {
     // get a new id
     _id = TRI_NewTickServer();
 
@@ -132,24 +150,7 @@ Result RocksDBTransactionState::beginTransaction(transaction::Hints hints) {
   } else {
     TRI_ASSERT(_status == transaction::Status::RUNNING);
   }
-
-  Result result = useCollections(_nestingLevel);
-
-  if (result.ok()) {
-    // all valid
-    if (_nestingLevel == 0) {
-      updateStatus(transaction::Status::RUNNING);
-    }
-  } else {
-    // something is wrong
-    if (_nestingLevel == 0) {
-      updateStatus(transaction::Status::ABORTED);
-    }
-
-    // free what we have got so far
-    unuseCollections(_nestingLevel);
-  }
-
+  
   return result;
 }
 
diff --git a/arangod/StorageEngine/TransactionCollection.h b/arangod/StorageEngine/TransactionCollection.h
index 3604dbb7bf..85900a141b 100644
--- a/arangod/StorageEngine/TransactionCollection.h
+++ b/arangod/StorageEngine/TransactionCollection.h
@@ -82,6 +82,10 @@ class TransactionCollection {
   virtual void release() = 0;
 
  protected:
+  inline bool isExclusive(AccessMode::Type type) const {
+    return (type == AccessMode::Type::EXCLUSIVE);
+  }
+  
   inline bool isWrite(AccessMode::Type type) const {
     return (type == AccessMode::Type::WRITE || type == AccessMode::Type::EXCLUSIVE);
   }