diff --git a/include/cbl/CBLCollection.h b/include/cbl/CBLCollection.h
index 070702ce..288f2fc3 100644
--- a/include/cbl/CBLCollection.h
+++ b/include/cbl/CBLCollection.h
@@ -155,12 +155,10 @@ CBLScope* CBLDatabase_DefaultScope(const CBLDatabase* db,
                                    CBLError* _cbl_nullable outError) CBLAPI;
 
 /** Returns the default collection.
-    @note  The default collection may not exist if it was deleted.
-           Also, the default collection cannot be recreated after being deleted.
     @note  You are responsible for releasing the returned collection.
     @param db  The database.
     @param outError  On failure, the error will be written here.
-    @return  A \ref CBLCollection instance, or NULL if the default collection doesn't exist or an error occurred. */
+    @return  A \ref CBLCollection instance, or NULL if an error occurred. */
 CBLCollection* _cbl_nullable CBLDatabase_DefaultCollection(const CBLDatabase* db,
                                                            CBLError* _cbl_nullable outError) CBLAPI;
 
diff --git a/src/CBLCollection.cc b/src/CBLCollection.cc
index f7b91481..c8f6e179 100644
--- a/src/CBLCollection.cc
+++ b/src/CBLCollection.cc
@@ -70,18 +70,8 @@ namespace cbl_internal {
             change.collection = _collection;
             change.docID = _docID;
 
-            Retained<CBLDatabase> db;
-            try {
-                db = _collection->database();
-            } catch (...) {
-                C4Error error = C4Error::fromCurrentException();
-                CBL_Log(kCBLLogDomainDatabase, kCBLLogWarning,
-                        "Document changed notification failed: %s", error.description().c_str());
-            }
-
-            if (db) {
-                db->notify(this, change);
-            }
+            auto db = _collection->database();
+            db->notify(this, change);
         }
 
         Retained<CBLCollection> _collection;
diff --git a/src/CBLCollection_CAPI.cc b/src/CBLCollection_CAPI.cc
index 89d2e8a5..a3610503 100644
--- a/src/CBLCollection_CAPI.cc
+++ b/src/CBLCollection_CAPI.cc
@@ -87,7 +87,7 @@ CBLScope* CBLDatabase_DefaultScope(const CBLDatabase* db, CBLError* outError) no
 
 CBLCollection* CBLDatabase_DefaultCollection(const CBLDatabase* db, CBLError* outError) noexcept {
     try {
-        return const_cast<CBLDatabase*>(db)->getDefaultCollection(false).detach();
+        return const_cast<CBLDatabase*>(db)->getDefaultCollection().detach();
     } catchAndBridge(outError)
 }
 
@@ -115,9 +115,7 @@ uint64_t CBLCollection_Count(const CBLCollection* collection) noexcept {
 
 /** Private API */
 CBLDatabase* CBLCollection_Database(const CBLCollection* collection) noexcept {
-    try {
-        return collection->database();
-    } catchAndWarn()
+    return collection->database();
 }
 
 /** Private API */
diff --git a/src/CBLCollection_Internal.hh b/src/CBLCollection_Internal.hh
index bc6817fc..43866766 100644
--- a/src/CBLCollection_Internal.hh
+++ b/src/CBLCollection_Internal.hh
@@ -36,9 +36,17 @@ public:
     CBLCollection(C4Collection* c4col, CBLScope* scope, CBLDatabase* database)
     :_c4col(c4col, database)
     ,_scope(scope)
+    ,_database(retain(database))
     ,_name(c4col->getName())
     { }
     
+    ~CBLCollection() {
+        LOCK(_adoptMutex);
+        if (!_adopted) {
+            release(_database);
+        }
+    }
+    
 #pragma mark - ACCESSORS:
     
     Retained<CBLScope> scope() const noexcept   {return _scope;}
@@ -47,9 +55,7 @@ public:
     bool isValid() const noexcept               {return _c4col.isValid();}
     uint64_t count() const                      {return _c4col.useLocked()->getDocumentCount();}
     uint64_t lastSequence() const               {return static_cast<uint64_t>(_c4col.useLocked()->getLastSequence());}
-    
-    /** Throw NotOpen if the collection or database is invalid */
-    CBLDatabase* database() const           {return _c4col.database();}
+    CBLDatabase* database() const               {return _database; }
     
 #pragma mark - DOCUMENTS:
     
@@ -161,17 +167,24 @@ protected:
     friend struct CBLDocument;
     friend struct cbl_internal::ListenerToken<CBLCollectionDocumentChangeListener>;
     
+    // Called by the database to take an ownership.
+    // Release the database to avoid the circular reference
+    void adopt(CBLDatabase* db) {
+        assert(_database == db);
+        LOCK(_adoptMutex);
+        if (!_adopted) {
+            _scope->adopt(db);
+            release(_database);
+            _adopted = true;
+        }
+    }
+    
     auto useLocked()                        { return _c4col.useLocked(); }
     template <class LAMBDA>
     void useLocked(LAMBDA callback)         { _c4col.useLocked(callback); }
     template <class RESULT, class LAMBDA>
     RESULT useLocked(LAMBDA callback)       { return _c4col.useLocked<RESULT>(callback); }
     
-    /** Called by the database when the database is released. */
-    void close() {
-        _c4col.close(); // This will invalidate the database pointer in the access lock
-    }
-    
 private:
     
     Retained<CBLDocument> getDocument(slice docID, bool isMutable, bool allRevisions) const {
@@ -204,18 +217,7 @@ private:
     }
     
     void collectionChanged() {
-        Retained<CBLDatabase> db;
-        try {
-            db = database();
-        } catch (...) {
-            C4Error error = C4Error::fromCurrentException();
-            CBL_Log(kCBLLogDomainDatabase, kCBLLogWarning,
-                    "Collection changed notification failed: %s", error.description().c_str());
-        }
-        
-        if (db) {
-            db->notify(std::bind(&CBLCollection::callCollectionChangeListeners, this));
-        }
+        _database->notify(std::bind(&CBLCollection::callCollectionChangeListeners, this));
     }
 
     void callCollectionChangeListeners() {
@@ -253,12 +255,10 @@ private:
         :shared_access_lock(std::move(c4col), *database->c4db())
         ,_c4db(database->c4db())
         ,_col(c4col)
-        ,_db(database)
         {
             _sentry = [this](C4Collection* c4col) {
                 if (!_isValid()) {
-                    C4Error::raise(LiteCoreDomain, kC4ErrorNotOpen,
-                                   "Invalid collection: either deleted, or db closed");
+                    C4Error::raise(LiteCoreDomain, kC4ErrorNotOpen, "Invalid collection: either deleted or db closed");
                 }
             };
         }
@@ -268,22 +268,11 @@ private:
             return _isValid();
         }
         
-        CBLDatabase* database() const {
-            auto lock = useLocked();
-            return _db;
-        }
-        
-        /** Invalidate the database pointer */
-        void close() noexcept {
-            LOCK_GUARD lock(getMutex());
-            _db = nullptr;
-        }
-        
     private:
-        bool _isValid() const noexcept                  { return _db && _col->isValid(); }
+        // Unsafe: need to call under lock:
+        bool _isValid() const noexcept                  { return !_c4db->isClosedNoLock() && _col->isValid(); }
         
         CBLDatabase::SharedC4DatabaseAccessLock _c4db;  // For retaining the shared lock
-        CBLDatabase* _cbl_nullable              _db;
         C4Collection*                           _col;
     };
     
@@ -294,6 +283,10 @@ private:
     alloc_slice                                             _name;
     Retained<CBLScope>                                      _scope;
     
+    CBLDatabase*                                            _database;         // Retained unless being adopted
+    bool                                                    _adopted {false};  // Adopted by the database
+    mutable std::mutex                                      _adoptMutex;
+    
     std::unique_ptr<C4CollectionObserver>                   _observer;
     Listeners<CBLCollectionChangeListener>                  _listeners;
     Listeners<CBLCollectionDocumentChangeListener>          _docListeners;
diff --git a/src/CBLDatabase.cc b/src/CBLDatabase.cc
index b76d018f..e2cc55e7 100644
--- a/src/CBLDatabase.cc
+++ b/src/CBLDatabase.cc
@@ -88,7 +88,6 @@ CBLDatabase::CBLDatabase(C4Database* _cbl_nonnull db, slice name_, slice dir_)
 ,_notificationQueue(this)
 {
     _c4db = std::make_shared<C4DatabaseAccessLock>(db);
-    _defaultCollection = getCollection(kC4DefaultCollectionName, kC4DefaultScopeID);
 }
 
 
@@ -129,14 +128,6 @@ void CBLDatabase::closeAndDelete() {
 
 /** Must called under _c4db lock. */
 void CBLDatabase::_closed() {
-    // Close scopes:
-    for (auto& i : _scopes) {
-        i.second->close();
-    }
-    // Close collections:
-    for (auto& i : _collections) {
-        i.second->close();
-    }
     // Close the access lock:
     _c4db->close();
 }
@@ -151,34 +142,11 @@ Retained<CBLScope> CBLDatabase::getScope(slice scopeName) {
     
     auto c4db = _c4db->useLocked();
     
-    CBLScope* scope = nullptr;
-    
     bool exist = c4db->hasScope(scopeName);
-    if (auto i = _scopes.find(scopeName); i != _scopes.end()) {
-        if (!exist) {
-            // Detach instead of close so that the retained scope
-            // object can retain the database and can be valid to use.
-            i->second->detach();
-            
-            // Remove from the _scopes map.
-            _scopes.erase(i);
-            
-            // Remove all collections in the scope from the _collections map:
-            // This is techically required to prevent circular reference
-            // (db->collection->scope->db) when the scope is detached.
-            removeCBLCollections(scopeName);
-            return nullptr;
-        }
-        scope = i->second.get();
-    }
-    
-    if (!scope && exist) {
-        auto retainedScope = make_retained<CBLScope>(scopeName, this);
-        scope = retainedScope.get();
-        _scopes.insert({scope->name(), std::move(retainedScope)});
+    if (!exist) {
+        return nullptr;
     }
-    
-    return scope;
+    return new CBLScope(scopeName, this);
 }
 
 
@@ -191,33 +159,13 @@ Retained<CBLCollection> CBLDatabase::getCollection(slice collectionName, slice s
     
     auto c4db = _c4db->useLocked();
     
-    CBLCollection* collection = nullptr;
     auto spec = C4Database::CollectionSpec(collectionName, scopeName);
-    if (auto i = _collections.find(spec); i != _collections.end()) {
-        collection = i->second.get();
-    }
-    
-    if (collection && collection->isValid()) {
-        return collection;
-    }
-    
     auto c4col = c4db->getCollection(spec);
     if (!c4col) {
-        if (collection) {
-            removeCBLCollection(spec); // Invalidate cache
-        }
         return nullptr;
     }
-    
-    auto scope = getScope(scopeName);
-    if (!scope) {
-        // Note (Edge Case):
-        // The scope is NULL because at the same time, its all collections including the
-        // the one just created were deleted on a different thread using another database.
-        return nullptr;
-    }
-    
-    return createCBLCollection(c4col, scope.get());
+    auto scope = new CBLScope(scopeName, this);
+    return new CBLCollection(c4col, scope, this);
 }
 
 
@@ -227,26 +175,10 @@ Retained<CBLCollection> CBLDatabase::createCollection(slice collectionName, slic
     
     auto c4db = _c4db->useLocked();
     
-    auto col = getCollection(collectionName, scopeName);
-    if (col) {
-        return col;
-    }
-    
     auto spec = C4Database::CollectionSpec(collectionName, scopeName);
     auto c4col = c4db->createCollection(spec);
-    
-    bool cache = true;
-    auto scope = getScope(scopeName);
-    if (!scope) {
-        // Note (Edge Case):
-        // The scope is NULL because at the same time, its all collections including the
-        // the one just created were deleted on a different thread using another database.
-        // So create the scope in non-cached mode, and the returned collection will not
-        // be cached.
-        cache = false;
-        scope = new CBLScope(scopeName, this, cache);
-    }
-    return createCBLCollection(c4col, scope.get(), cache);
+    auto scope = new CBLScope(scopeName, this);
+    return new CBLCollection(c4col, scope, this);
 }
 
 
@@ -258,60 +190,26 @@ bool CBLDatabase::deleteCollection(slice collectionName, slice scopeName) {
     
     auto spec = C4Database::CollectionSpec(collectionName, scopeName);
     c4db->deleteCollection(spec);
-    removeCBLCollection(spec);
     return true;
 }
 
 
 Retained<CBLScope> CBLDatabase::getDefaultScope() {
-    _c4db->useLocked();
     return getScope(kC4DefaultScopeID);
 }
 
 
-Retained<CBLCollection> CBLDatabase::getDefaultCollection(bool mustExist) {
-    auto db = _c4db->useLocked();
-    
-    if (_defaultCollection && !_defaultCollection->isValid()) {
-        _defaultCollection = nullptr;
-    }
-    
-    if (!_defaultCollection && mustExist) {
-        C4Error::raise(LiteCoreDomain, kC4ErrorNotOpen,
-                       "Invalid collection: either deleted, or db closed");
-    }
-    
-    return _defaultCollection;
+Retained<CBLCollection> CBLDatabase::getDefaultCollection() {
+    return getCollection(kC4DefaultCollectionName, kC4DefaultScopeID);
 }
 
 
-Retained<CBLCollection> CBLDatabase::createCBLCollection(C4Collection* c4col, CBLScope* scope, bool cache) {
-    auto retainedCollection = make_retained<CBLCollection>(c4col, scope, const_cast<CBLDatabase*>(this));
-    auto collection = retainedCollection.get();
-    if (cache) {
-        _collections.insert({C4Database::CollectionSpec(c4col->getSpec()), std::move(retainedCollection)});
-    }
-    return collection;
-}
-
-
-void CBLDatabase::removeCBLCollection(C4Database::CollectionSpec spec) {
-    if (auto i = _collections.find(spec); i != _collections.end()) {
-        i->second.get()->close();
-        _collections.erase(i);
-    }
-}
-
-void CBLDatabase::removeCBLCollections(slice scopeName) {
-    auto i = _collections.begin();
-    while (i != _collections.end()) {
-        if (i->first.scope == scopeName) {
-            i->second->close();
-            i = _collections.erase(i);
-        } else {
-            i++;
-        }
+Retained<CBLCollection> CBLDatabase::getInternalDefaultCollection() {
+    if (!_defaultCollection) {
+        _defaultCollection = getCollection(kC4DefaultCollectionName, kC4DefaultScopeID);
+        _defaultCollection->adopt(this); // Prevent the retain cycle
     }
+    return _defaultCollection;
 }
 
 
diff --git a/src/CBLDatabase_CAPI.cc b/src/CBLDatabase_CAPI.cc
index bc914dcd..d61ad4bb 100644
--- a/src/CBLDatabase_CAPI.cc
+++ b/src/CBLDatabase_CAPI.cc
@@ -142,7 +142,7 @@ const CBLDatabaseConfiguration CBLDatabase_Config(const CBLDatabase* db) noexcep
 
 uint64_t CBLDatabase_Count(const CBLDatabase* db) noexcept {
     try {
-        auto col = const_cast<CBLDatabase*>(db)->getDefaultCollection(true);
+        auto col = const_cast<CBLDatabase*>(db)->getInternalDefaultCollection();
         return col->count();
     } catchAndWarn();
 }
@@ -150,7 +150,7 @@ uint64_t CBLDatabase_Count(const CBLDatabase* db) noexcept {
 /** Private API */
 uint64_t CBLDatabase_LastSequence(const CBLDatabase* db) noexcept {
     try {
-        auto col = const_cast<CBLDatabase*>(db)->getDefaultCollection(true);
+        auto col = const_cast<CBLDatabase*>(db)->getInternalDefaultCollection();
         return col->lastSequence();
     } catchAndWarn()
 }
@@ -163,7 +163,7 @@ const CBLDocument* CBLDatabase_GetDocument(const CBLDatabase* db, FLString docID
                                            CBLError* outError) noexcept
 {
     try {
-        auto col = const_cast<CBLDatabase*>(db)->getDefaultCollection(true);
+        auto col = const_cast<CBLDatabase*>(db)->getInternalDefaultCollection();
         return CBLCollection_GetDocument(col, docID, outError);
     } catchAndBridge(outError)
 }
@@ -173,7 +173,7 @@ CBLDocument* CBLDatabase_GetMutableDocument(CBLDatabase* db, FLString docID,
                                             CBLError* outError) noexcept
 {
     try {
-        auto col = db->getDefaultCollection(true);
+        auto col = db->getInternalDefaultCollection();
         return CBLCollection_GetMutableDocument(col, docID, outError);
     } catchAndBridge(outError)
 }
@@ -193,7 +193,7 @@ bool CBLDatabase_SaveDocumentWithConcurrencyControl(CBLDatabase* db,
                                                     CBLError* outError) noexcept
 {
     try {
-        auto col = db->getDefaultCollection(true);
+        auto col = db->getInternalDefaultCollection();
         return CBLCollection_SaveDocumentWithConcurrencyControl(col, doc, concurrency, outError);
     } catchAndBridge(outError)
 }
@@ -205,7 +205,7 @@ bool CBLDatabase_SaveDocumentWithConflictHandler(CBLDatabase* db,
                                                  CBLError* outError) noexcept
 {
     try {
-        auto col = db->getDefaultCollection(true);
+        auto col = db->getInternalDefaultCollection();
         return CBLCollection_SaveDocumentWithConflictHandler(col, doc, conflictHandler,
                                                              context, outError);
     } catchAndBridge(outError)
@@ -216,7 +216,7 @@ bool CBLDatabase_DeleteDocument(CBLDatabase *db,
                                 CBLError* outError) noexcept
 {
     try {
-        auto col = db->getDefaultCollection(true);
+        auto col = db->getInternalDefaultCollection();
         return CBLCollection_DeleteDocument(col, doc, outError);
     } catchAndBridge(outError)
 }
@@ -227,7 +227,7 @@ bool CBLDatabase_DeleteDocumentWithConcurrencyControl(CBLDatabase *db,
                                                       CBLError* outError) noexcept
 {
     try {
-        auto col = db->getDefaultCollection(true);
+        auto col = db->getInternalDefaultCollection();
         return CBLCollection_DeleteDocumentWithConcurrencyControl(col, doc, concurrency, outError);
     } catchAndBridge(outError)
 }
@@ -238,7 +238,7 @@ bool CBLDatabase_DeleteDocumentByID(CBLDatabase* db,
                                     CBLError* outError) noexcept
 {
     try {
-        auto col = db->getDefaultCollection(true);
+        auto col = db->getInternalDefaultCollection();
         return CBLCollection_DeleteDocumentByID(col, docID, outError);
     } catchAndBridge(outError)
 }
@@ -248,7 +248,7 @@ bool CBLDatabase_PurgeDocument(CBLDatabase* db,
                                CBLError* outError) noexcept
 {
     try {
-        auto col = db->getDefaultCollection(true);
+        auto col = db->getInternalDefaultCollection();
         CBLDocument::checkCollectionMatches(doc->collection(), col);
         return CBLCollection_PurgeDocumentByID(col, doc->docID(), outError);
     } catchAndBridge(outError)
@@ -260,7 +260,7 @@ bool CBLDatabase_PurgeDocumentByID(CBLDatabase* db,
                                    CBLError* outError) noexcept
 {
     try {
-        auto col = db->getDefaultCollection(true);
+        auto col = db->getInternalDefaultCollection();
         return CBLCollection_PurgeDocumentByID(col, docID, outError);
     } catchAndBridge(outError)
 }
@@ -270,7 +270,7 @@ CBLTimestamp CBLDatabase_GetDocumentExpiration(CBLDatabase* db,
                                                CBLError* outError) noexcept
 {
     try {
-        auto col = db->getDefaultCollection(true);
+        auto col = db->getInternalDefaultCollection();
         return CBLCollection_GetDocumentExpiration(col, docID, outError);
     } catchAndBridge(outError)
 }
@@ -281,7 +281,7 @@ bool CBLDatabase_SetDocumentExpiration(CBLDatabase* db,
                                        CBLError* outError) noexcept
 {
     try {
-        auto col = db->getDefaultCollection(true);
+        auto col = db->getInternalDefaultCollection();
         return CBLCollection_SetDocumentExpiration(col, docID, expiration, outError);
     } catchAndBridge(outError)
 }
@@ -296,7 +296,7 @@ bool CBLDatabase_CreateValueIndex(CBLDatabase *db,
                                   CBLError *outError) noexcept
 {
     try {
-        auto col = db->getDefaultCollection(true);
+        auto col = db->getInternalDefaultCollection();
         return CBLCollection_CreateValueIndex(col, name, config, outError);
     } catchAndBridge(outError)
 }
@@ -308,7 +308,7 @@ bool CBLDatabase_CreateFullTextIndex(CBLDatabase *db,
                                      CBLError *outError) noexcept
 {
     try {
-        auto col = db->getDefaultCollection(true);
+        auto col = db->getInternalDefaultCollection();
         return CBLCollection_CreateFullTextIndex(col, name, config, outError);
     } catchAndBridge(outError)
 }
@@ -319,7 +319,7 @@ bool CBLDatabase_DeleteIndex(CBLDatabase *db,
                              CBLError *outError) noexcept
 {
     try {
-        auto col = db->getDefaultCollection(true);
+        auto col = db->getInternalDefaultCollection();
         return CBLCollection_DeleteIndex(col, name, outError);
     } catchAndBridge(outError)
 }
@@ -327,7 +327,7 @@ bool CBLDatabase_DeleteIndex(CBLDatabase *db,
 
 FLArray CBLDatabase_GetIndexNames(CBLDatabase *db) noexcept {
     try {
-        auto col = db->getDefaultCollection(true);
+        auto col = db->getInternalDefaultCollection();
         
         CBLError error;
         auto result = CBLCollection_GetIndexNames(col, &error);
@@ -380,7 +380,7 @@ CBLListenerToken* CBLDatabase_AddChangeListener(const CBLDatabase* db,
     };
 
     try {
-        CBLCollection* col = const_cast<CBLDatabase*>(db)->getDefaultCollection(true).detach();
+        CBLCollection* col = const_cast<CBLDatabase*>(db)->getInternalDefaultCollection().detach();
         wrappedContext->collection = col;
         
         auto token = CBLCollection_AddChangeListener(col, wrappedListener, wrappedContext);
@@ -421,7 +421,7 @@ CBLListenerToken* CBLDatabase_AddDocumentChangeListener(const CBLDatabase* db,
     };
     
     try {
-        CBLCollection* col = const_cast<CBLDatabase*>(db)->getDefaultCollection(true).detach();
+        CBLCollection* col = const_cast<CBLDatabase*>(db)->getInternalDefaultCollection().detach();
         wrappedContext->collection = col;
         
         auto token = CBLCollection_AddDocumentChangeListener(col, docID, wrappedListener, wrappedContext);
diff --git a/src/CBLDatabase_Internal.hh b/src/CBLDatabase_Internal.hh
index 5a0a8a07..01eeb54b 100644
--- a/src/CBLDatabase_Internal.hh
+++ b/src/CBLDatabase_Internal.hh
@@ -154,11 +154,12 @@ public:
     
     Retained<CBLScope> getDefaultScope();
     
+    Retained<CBLCollection> getDefaultCollection();
+    
     /**
-     * Returned the default collection retained by the database. It will be used for any database's operations
-     * that refer to the default collection. If the default collection doesn't exist when getting from the database,
-     * the method will throw kC4ErrorNotOpen exception. */
-    Retained<CBLCollection> getDefaultCollection(bool mustExist);
+     * The cached default collection for internal use only.
+     */
+    Retained<CBLCollection> getInternalDefaultCollection();
     
 
 #pragma mark - Queries & Indexes:
@@ -215,7 +216,7 @@ protected:
         :access_lock(std::move(db))
         {
             _sentry = [this](C4Database* db) {
-                if (_closed) {
+                if (isClosedNoLock()) {
                     C4Error::raise(LiteCoreDomain, kC4ErrorNotOpen, "Database is closed or deleted");
                 }
             };
@@ -226,6 +227,10 @@ protected:
             _closed = true;
         }
         
+        bool isClosedNoLock() {
+            return _closed;
+        }
+        
         template <class CALLBACK>
         /** If the AccessLock is closed, the call will be ignored instead of letting the sentry throws. */
         void useLockedIgnoredWhenClosed(CALLBACK callback) {
@@ -315,17 +320,6 @@ private:
         }
     }
 
-    /**
-     Create a CBLCollection from the C4Collection.
-     The created CBLCollection will be retained and cached in the _collections map. */
-    Retained<CBLCollection> createCBLCollection(C4Collection* c4col, CBLScope* scope, bool cache= true);
-    
-    /** Remove and close the collection from the _collections map */
-    void removeCBLCollection(C4Database::CollectionSpec spec);
-    
-    /** Remove and close all collections in the specify scope the _collections map */
-    void removeCBLCollections(slice scopeName);
-
     void callDocListeners();
     
     void stopActiveStoppables() {
@@ -386,9 +380,7 @@ private:
     alloc_slice const                           _name;
     alloc_slice const                           _dir;
     
-    mutable ScopesMap                           _scopes;
-    mutable CollectionsMap                      _collections;
-    Retained<CBLCollection>                     _defaultCollection;
+    Retained<CBLCollection>                     _defaultCollection;     // Internal default collection
     
     // For sending notifications:
     NotificationQueue                           _notificationQueue;
diff --git a/src/CBLDocument.cc b/src/CBLDocument.cc
index b2650a3d..7c61033f 100644
--- a/src/CBLDocument.cc
+++ b/src/CBLDocument.cc
@@ -68,7 +68,6 @@ CBLDocument::~CBLDocument() {
 
 
 CBLDatabase* _cbl_nullable CBLDocument::database() const {
-    // Could throw kC4ErrorNotOpen if the collection is deleted, or database is released.
     return _collection ? _collection->database() : nullptr;
 }
 
diff --git a/src/CBLPrivate.h b/src/CBLPrivate.h
index 355bc19d..fe22f1a1 100644
--- a/src/CBLPrivate.h
+++ b/src/CBLPrivate.h
@@ -28,8 +28,8 @@ CBL_CAPI_BEGIN
     void CBLLog_BeginExpectingExceptions() CBLAPI;
     void CBLLog_EndExpectingExceptions() CBLAPI;
 
-/** Returns the collection's database, or NULL if the collection is invalid, or the database is released. */
-    CBLDatabase* _cbl_nullable CBLCollection_Database(const CBLCollection*) CBLAPI;
+/** Returns the collection's database, */
+    CBLDatabase* CBLCollection_Database(const CBLCollection*) CBLAPI;
 
 /** Returns the last sequence number assigned in the database (default collection).
     This starts at zero and increments every time a document is saved or deleted. */
diff --git a/src/CBLReplicator_CAPI.cc b/src/CBLReplicator_CAPI.cc
index 8e3ca5e1..6a8752f9 100644
--- a/src/CBLReplicator_CAPI.cc
+++ b/src/CBLReplicator_CAPI.cc
@@ -84,14 +84,22 @@ void CBLReplicator_SetSuspended(CBLReplicator* repl, bool sus) noexcept   {repl-
 
 FLDict CBLReplicator_PendingDocumentIDs(CBLReplicator *repl, CBLError *outError) noexcept {
     try {
-        auto col = repl->database()->getDefaultCollection(true);
+        auto col = repl->defaultCollection();
+        if (!col) {
+            C4Error::raise(LiteCoreDomain, kC4ErrorInvalidParameter,
+                           "The default collection is not included in the replicator config.");
+        }
         return CBLReplicator_PendingDocumentIDs2(repl, col, outError);
     } catchAndBridge(outError)
 }
 
 bool CBLReplicator_IsDocumentPending(CBLReplicator *repl, FLString docID, CBLError *outError) noexcept {
     try {
-        auto col = repl->database()->getDefaultCollection(true);
+        auto col = repl->defaultCollection();
+        if (!col) {
+            C4Error::raise(LiteCoreDomain, kC4ErrorInvalidParameter,
+                           "The default collection is not included in the replicator config.");
+        }
         return CBLReplicator_IsDocumentPending2(repl, docID, col, outError);
     } catchAndBridge(outError)
 }
diff --git a/src/CBLReplicator_Internal.hh b/src/CBLReplicator_Internal.hh
index 9ddf7435..5d8d4013 100644
--- a/src/CBLReplicator_Internal.hh
+++ b/src/CBLReplicator_Internal.hh
@@ -72,7 +72,7 @@ public:
         call_once(once, std::bind(&C4RegisterBuiltInWebSocket));
         
         if (_conf.database) {
-            _defaultCollection = _conf.database->getDefaultCollection(true);
+            _defaultCollection = _conf.database->getInternalDefaultCollection();
         }
 
         _conf.validate();
@@ -237,9 +237,21 @@ public:
         _stoppable = make_unique<CBLReplicatorStoppable>(this);
     }
     
+    CBLCollection* _cbl_nullable defaultCollection() {
+        if (_defaultCollection) {
+            return _defaultCollection;
+        }
+        
+        if (auto i = _collections.find(kC4DefaultCollectionSpec); i != _collections.end()) {
+            return i->second.collection;
+        }
+        
+        return nullptr;
+    }
 
     const ReplicatorConfiguration* configuration() const    {return &_conf;}
     CBLDatabase* database() const                           {return _db;}
+    
     void setHostReachable(bool reachable)                   {_c4repl->setHostReachable(reachable);}
     void setSuspended(bool suspended)                       {_c4repl->setSuspended(suspended);}
     void stop()                                             {_c4repl->stop();}
diff --git a/src/CBLScope.cc b/src/CBLScope.cc
index c5d449df..b0d0f821 100644
--- a/src/CBLScope.cc
+++ b/src/CBLScope.cc
@@ -23,6 +23,5 @@ using namespace fleece;
 
 Retained<CBLCollection> CBLScope::getCollection(slice collectionName) const {
     LOCK(_mutex);
-    checkOpen();
     return _database->getCollection(collectionName, _name);
 }
diff --git a/src/CBLScope_Internal.hh b/src/CBLScope_Internal.hh
index fb06feec..f62f92b3 100644
--- a/src/CBLScope_Internal.hh
+++ b/src/CBLScope_Internal.hh
@@ -29,18 +29,14 @@ public:
     
 #pragma mark - CONSTRUCTORS:
     
-    CBLScope(slice name, CBLDatabase* database, bool cached= true)
+    CBLScope(slice name, CBLDatabase* database)
     :_name(name)
-    ,_database(database)
-    {
-        if (!cached) {
-            _detach();
-        }
-    }
+    ,_database(retain(database))
+    { }
     
     ~CBLScope() {
         LOCK(_mutex);
-        if (_detached) {
+        if (!_adopted) {
             release(_database);
         }
     }
@@ -52,8 +48,6 @@ public:
 #pragma mark - COLLECTIONS:
     
     fleece::MutableArray collectionNames() const {
-        LOCK(_mutex);
-        checkOpen();
         return _database->collectionNames(_name);
     }
     
@@ -61,45 +55,27 @@ public:
     
 protected:
     
-    friend struct CBLDatabase;
+    friend struct CBLCollection;
     
-    // Need to call under the _mutex lock
-    void checkOpen() const {
-        if (!_database) {
-            C4Error::raise(LiteCoreDomain, kC4ErrorNotOpen,
-                           "Invalid scope: scope deleted or db closed");
-        }
-    }
-    
-    // Called by database when the database is closed or released
-    // to invalidate the database pointer.
-    void close() {
+    // Called by the collection to give the ownership to the database
+    // when the collection is adopted by the database.
+    // Release the database to avoid the circular reference
+    void adopt(CBLDatabase* db) {
+        assert(_database == db);
         LOCK(_mutex);
-        assert(!_detached);
-        _database = nullptr;
-    }
-    
-    // Called by the database when the scope is removed from
-    // the database cache (e.g. when no collections are in the scope).
-    // The detach() allows the scope to retain and keep using the database.
-    void detach() {
-        LOCK(_mutex);
-        _detach();
+        if (!_adopted) {
+            release(_database);
+            _adopted = true;
+        }
     }
     
 private:
     
-    void _detach() {
-        assert(!_detached);
-        retain(_database);
-        _detached = true;
-    }
-    
-    CBLDatabase* _cbl_nullable              _database;
-    bool                                    _detached {false};  // Detached mode in which database is retained
+    CBLDatabase*                            _database;          // Retained unless being adopted
+    bool                                    _adopted {false};   // Adopted by the database
     
     alloc_slice const                       _name;              // Name (never empty)
-    mutable std::recursive_mutex            _mutex;
+    mutable std::mutex                      _mutex;
 };
 
 CBL_ASSUME_NONNULL_END
diff --git a/test/CollectionTest.cc b/test/CollectionTest.cc
index fdbad312..61e0a503 100644
--- a/test/CollectionTest.cc
+++ b/test/CollectionTest.cc
@@ -399,8 +399,6 @@ TEST_CASE_METHOD(CollectionTest, "Create Existing Collection", "[Collection]") {
     REQUIRE(col2);
     CHECK(CBLCollection_Name(col2) == "colA"_sl);
     
-    CHECK(col1 == col2);
-    
     CBLCollection_Release(col1);
     CBLCollection_Release(col2);
 }
@@ -462,10 +460,10 @@ TEST_CASE_METHOD(CollectionTest, "Get Collections from Scope", "[Collection]") {
     CHECK(CBLScope_Name(scope) == "scopeA"_sl);
     
     CBLCollection* colA2 = CBLScope_Collection(scope, "colA"_sl, &error);
-    CHECK(colA == colA2);
+    CHECK(CBLCollection_Name(colA2) == "colA"_sl);
     
     CBLCollection* colB2 = CBLScope_Collection(scope, "colB"_sl, &error);
-    CHECK(colB == colB2);
+    CHECK(CBLCollection_Name(colB2) == "colB"_sl);
     
     CHECK(!CBLScope_Collection(scope, "colC"_sl, &error));
     CHECK(error.code == 0);
@@ -540,8 +538,6 @@ TEST_CASE_METHOD(CollectionTest, "Valid Collection and Scope Names", "[Collectio
         CBLCollection* col2 = CBLDatabase_Collection(db, slice(name), slice(name), &error);
         REQUIRE(col2);
         
-        CHECK(col1 == col2);
-        
         CBLCollection_Release(col1);
         CBLCollection_Release(col2);
     }
diff --git a/test/CollectionTest_Cpp.cc b/test/CollectionTest_Cpp.cc
index 4a910d88..7626722b 100644
--- a/test/CollectionTest_Cpp.cc
+++ b/test/CollectionTest_Cpp.cc
@@ -232,7 +232,6 @@ TEST_CASE_METHOD(CollectionTest_Cpp, "C++ Create Existing Collection", "[Collect
     REQUIRE(col2);
     CHECK(col2.name() == "colA");
     CHECK(col2.scopeName() == "scopeA");
-    CHECK(col1 == col2);
 }
 
 TEST_CASE_METHOD(CollectionTest_Cpp, "C++ Delete Collection", "[Collection]") {
diff --git a/test/LogTest.cc b/test/LogTest.cc
index 976aed3c..1001238b 100644
--- a/test/LogTest.cc
+++ b/test/LogTest.cc
@@ -260,7 +260,7 @@ TEST_CASE_METHOD(LogTest, "File Logging : Set Log Level", "[Log][FileLog]") {
     }
     
     // Verify:
-    int lineCount = 1; // Header:
+    int lineCount = 2; // 2 header lines :
     for (CBLLogLevel level : kLogLevels) {
         if (level == kCBLLogNone)
             continue;
diff --git a/test/QueryTest.cc b/test/QueryTest.cc
index e6500540..56a7b94e 100644
--- a/test/QueryTest.cc
+++ b/test/QueryTest.cc
@@ -505,7 +505,7 @@ TEST_CASE_METHOD(QueryTest, "Query Listener", "[Query][LiveQuery]") {
     
     cerr << "Adding listener\n";
     ListenerState state;
-    auto listenerToken = CBLQuery_AddChangeListener(query, [](void *context, CBLQuery* query, CBLListenerToken* token) {
+    CBLListenerToken* listenerToken = CBLQuery_AddChangeListener(query, [](void *context, CBLQuery* query, CBLListenerToken* token) {
         ((ListenerState*)context)->receivedCallback(context, query, token);
     }, &state);
 
@@ -543,7 +543,7 @@ TEST_CASE_METHOD(QueryTest, "Remove Query Listener", "[Query][LiveQuery]") {
     
     cerr << "Adding listener\n";
     ListenerState state;
-    auto listenerToken = CBLQuery_AddChangeListener(query, [](void *context, CBLQuery* query, CBLListenerToken* token) {
+    CBLListenerToken*  listenerToken = CBLQuery_AddChangeListener(query, [](void *context, CBLQuery* query, CBLListenerToken* token) {
         ((ListenerState*)context)->receivedCallback(context, query, token);
     }, &state);
 
@@ -585,7 +585,7 @@ TEST_CASE_METHOD(QueryTest, "Query Listener and Changing parameters", "[Query][L
 
     cerr << "Adding listener\n";
     ListenerState state;
-    auto listenerToken = CBLQuery_AddChangeListener(query, [](void *context, CBLQuery* query, CBLListenerToken* token) {
+    CBLListenerToken* listenerToken = CBLQuery_AddChangeListener(query, [](void *context, CBLQuery* query, CBLListenerToken* token) {
         ((ListenerState*)context)->receivedCallback(context, query, token);
     }, &state);
 
@@ -623,10 +623,10 @@ TEST_CASE_METHOD(QueryTest, "Multiple Query Listeners", "[Query][LiveQuery]") {
     
     cerr << "Adding listener\n";
     ListenerState state1;
-    auto token1 = CBLQuery_AddChangeListener(query, callback, &state1);
+    CBLListenerToken* token1 = CBLQuery_AddChangeListener(query, callback, &state1);
     
     ListenerState state2;
-    auto token2 = CBLQuery_AddChangeListener(query, callback, &state2);
+    CBLListenerToken* token2 = CBLQuery_AddChangeListener(query, callback, &state2);
 
     cerr << "Waiting for listener 1...\n";
     state1.waitForCount(1);
@@ -654,7 +654,7 @@ TEST_CASE_METHOD(QueryTest, "Multiple Query Listeners", "[Query][LiveQuery]") {
     
     cerr << "Adding another listener\n";
     ListenerState state3;
-    auto token3 = CBLQuery_AddChangeListener(query, callback, &state3);
+    CBLListenerToken* token3 = CBLQuery_AddChangeListener(query, callback, &state3);
     
     cerr << "Waiting for the listener 3...\n";
     state3.waitForCount(1);
@@ -684,7 +684,7 @@ TEST_CASE_METHOD(QueryTest, "Query Listener and Coalescing notification", "[Quer
     
     cerr << "Adding listener\n";
     ListenerState state;
-    auto listenerToken = CBLQuery_AddChangeListener(query, [](void *context, CBLQuery* query, CBLListenerToken* token) {
+    CBLListenerToken* listenerToken = CBLQuery_AddChangeListener(query, [](void *context, CBLQuery* query, CBLListenerToken* token) {
         ((ListenerState*)context)->receivedCallback(context, query, token);
     }, &state);
 
@@ -970,14 +970,14 @@ TEST_CASE_METHOD(QueryTest, "FTS with FTS Index in Named Collection", "[Query]")
     createDocWithJSON(people, "person2", "{\"name\": { \"first\": \"Jasper\",\"last\":\"Okorududu\"}, \"random\": \"1\"}");
     createDocWithJSON(people, "person3", "{\"name\": { \"first\": \"Monica\",\"last\":\"Polina\"}, \"random\": \"2\"}");
 
-    CBLCollection_Release(people);
-
     CBLFullTextIndexConfiguration index = {};
     index.expressionLanguage = kCBLN1QLLanguage;
     index.expressions = "name.first"_sl;
     index.ignoreAccents = false;
     CHECK(CBLCollection_CreateFullTextIndex(people, "index"_sl, index, &error));
 
+    CBLCollection_Release(people);
+    
     SECTION("name"){
         queryString = "SELECT name "
                       "FROM test.people "
diff --git a/vendor/couchbase-lite-core b/vendor/couchbase-lite-core
index 20bf8565..476a079a 160000
--- a/vendor/couchbase-lite-core
+++ b/vendor/couchbase-lite-core
@@ -1 +1 @@
-Subproject commit 20bf8565c434def7ce4d82824e54971e69d0595c
+Subproject commit 476a079a57ab4076c927ed3a0e81cd50a54b1cbd