diff --git a/pkg/acl/acltree/acltree.go b/pkg/acl/acltree/acltree.go
index 49e530db..5cd85957 100644
--- a/pkg/acl/acltree/acltree.go
+++ b/pkg/acl/acltree/acltree.go
@@ -2,6 +2,7 @@ package acltree
 
 import (
 	"context"
+	"errors"
 	"github.com/anytypeio/go-anytype-infrastructure-experiments/pkg/acl/account"
 	"github.com/anytypeio/go-anytype-infrastructure-experiments/pkg/acl/aclchanges/aclpb"
 	"github.com/anytypeio/go-anytype-infrastructure-experiments/pkg/acl/treestorage"
@@ -35,7 +36,16 @@ func (n NoOpListener) Update(tree ACLTree) {}
 
 func (n NoOpListener) Rebuild(tree ACLTree) {}
 
+type RWLocker interface {
+	sync.Locker
+	RLock()
+	RUnlock()
+}
+
+var ErrNoCommonSnapshot = errors.New("trees doesn't have a common snapshot")
+
 type ACLTree interface {
+	RWLocker
 	ACLState() *ACLState
 	AddContent(ctx context.Context, f func(builder ChangeBuilder) error) (*Change, error)
 	AddRawChanges(ctx context.Context, changes ...*aclpb.RawChange) (AddResult, error)
@@ -45,6 +55,7 @@ type ACLTree interface {
 	IterateFrom(string, func(change *Change) bool)
 	HasChange(string) bool
 	SnapshotPath() []string
+	ChangesAfterCommonSnapshot(snapshotPath []string) ([]*aclpb.RawChange, error)
 
 	Close() error
 }
@@ -204,17 +215,12 @@ func (a *aclTree) rebuildFromStorage(fromStart bool) error {
 }
 
 func (a *aclTree) ACLState() *ACLState {
-	// TODO: probably locks should be happening outside because we are using object cache
-	a.RLock()
-	defer a.RUnlock()
 	return a.aclState
 }
 
 func (a *aclTree) AddContent(ctx context.Context, build func(builder ChangeBuilder) error) (*Change, error) {
 	// TODO: add snapshot creation logic
-	a.Lock()
 	defer func() {
-		a.Unlock()
 		// TODO: should this be called in a separate goroutine to prevent accidental cycles (tree->updater->tree)
 		a.updateListener.Update(a)
 	}()
@@ -248,7 +254,6 @@ func (a *aclTree) AddContent(ctx context.Context, build func(builder ChangeBuild
 }
 
 func (a *aclTree) AddRawChanges(ctx context.Context, rawChanges ...*aclpb.RawChange) (AddResult, error) {
-	a.Lock()
 	// TODO: make proper error handling, because there are a lot of corner cases where this will break
 	var err error
 	var mode Mode
@@ -278,7 +283,6 @@ func (a *aclTree) AddRawChanges(ctx context.Context, rawChanges ...*aclpb.RawCha
 			return
 		}
 
-		a.Unlock()
 		switch mode {
 		case Append:
 			a.updateListener.Update(a)
@@ -350,20 +354,14 @@ func (a *aclTree) AddRawChanges(ctx context.Context, rawChanges ...*aclpb.RawCha
 }
 
 func (a *aclTree) Iterate(f func(change *Change) bool) {
-	a.RLock()
-	defer a.RUnlock()
 	a.fullTree.Iterate(a.fullTree.RootId(), f)
 }
 
 func (a *aclTree) IterateFrom(s string, f func(change *Change) bool) {
-	a.RLock()
-	defer a.RUnlock()
 	a.fullTree.Iterate(s, f)
 }
 
 func (a *aclTree) HasChange(s string) bool {
-	a.RLock()
-	defer a.RUnlock()
 	_, attachedExists := a.fullTree.attached[s]
 	_, unattachedExists := a.fullTree.unAttached[s]
 	_, invalidExists := a.fullTree.invalidChanges[s]
@@ -371,14 +369,10 @@ func (a *aclTree) HasChange(s string) bool {
 }
 
 func (a *aclTree) Heads() []string {
-	a.RLock()
-	defer a.RUnlock()
 	return a.fullTree.Heads()
 }
 
 func (a *aclTree) Root() *Change {
-	a.RLock()
-	defer a.RUnlock()
 	return a.fullTree.Root()
 }
 
@@ -387,8 +381,7 @@ func (a *aclTree) Close() error {
 }
 
 func (a *aclTree) SnapshotPath() []string {
-	a.RLock()
-	defer a.RUnlock()
+	// TODO: think about caching this
 
 	var path []string
 	// TODO: think that the user may have not all of the snapshots locally
@@ -403,3 +396,63 @@ func (a *aclTree) SnapshotPath() []string {
 	}
 	return path
 }
+
+func (a *aclTree) ChangesAfterCommonSnapshot(theirPath []string) ([]*aclpb.RawChange, error) {
+	// TODO: think about when the clients will have their full acl tree and thus full snapshots
+	//  but no changes after some of the snapshots
+	commonSnapshot, err := a.commonSnapshotForTwoPaths(a.SnapshotPath(), theirPath)
+	if err != nil {
+		return nil, err
+	}
+	// we presume that we have everything after the common snapshot, though this may not be the case in case of clients and only ACL tree changes
+	changes, err := a.treeBuilder.dfs(a.fullTree.Heads(), commonSnapshot, func(id string) (*Change, error) {
+		// using custom load function to skip verification step and save raw changes
+		raw, err := a.treeStorage.GetChange(context.Background(), id)
+		if err != nil {
+			return nil, err
+		}
+
+		aclChange, err := a.treeBuilder.makeUnverifiedACLChange(raw)
+		if err != nil {
+			return nil, err
+		}
+
+		ch := NewChange(id, aclChange)
+		ch.Raw = raw
+		return ch, nil
+	})
+	if err != nil {
+		return nil, err
+	}
+	var rawChanges []*aclpb.RawChange
+	for _, ch := range changes {
+		rawChanges = append(rawChanges, ch.Raw)
+	}
+	return rawChanges, nil
+}
+
+func (a *aclTree) commonSnapshotForTwoPaths(ourPath []string, theirPath []string) (string, error) {
+	var i int
+	var j int
+OuterLoop:
+	// find starting point from the right
+	for i = len(ourPath) - 1; i >= 0; i-- {
+		for j = len(theirPath) - 1; j >= 0; j-- {
+			// most likely there would be only one comparison, because mostly the snapshot path will start from the root for nodes
+			if ourPath[i] == theirPath[j] {
+				break OuterLoop
+			}
+		}
+	}
+	if i < 0 || j < 0 {
+		return "", ErrNoCommonSnapshot
+	}
+	// find last common element of the sequence moving from right to left
+	for i >= 0 && j >= 0 {
+		if ourPath[i] == theirPath[j] {
+			i--
+			j--
+		}
+	}
+	return ourPath[i+1], nil
+}
diff --git a/pkg/acl/acltree/change.go b/pkg/acl/acltree/change.go
index c768ef23..67eedf00 100644
--- a/pkg/acl/acltree/change.go
+++ b/pkg/acl/acltree/change.go
@@ -23,6 +23,7 @@ type Change struct {
 	SnapshotId              string
 	IsSnapshot              bool
 	DecryptedDocumentChange []byte
+	Raw                     *aclpb.RawChange // this will not be present on all changes, we only need it sometimes
 
 	Content *aclpb.ACLChange
 	Sign    []byte
diff --git a/pkg/acl/acltree/changeloader.go b/pkg/acl/acltree/changeloader.go
index d3b57a32..b308397a 100644
--- a/pkg/acl/acltree/changeloader.go
+++ b/pkg/acl/acltree/changeloader.go
@@ -91,3 +91,9 @@ func (c *changeLoader) makeVerifiedACLChange(change *aclpb.RawChange) (aclChange
 	}
 	return
 }
+
+func (c *changeLoader) makeUnverifiedACLChange(change *aclpb.RawChange) (aclChange *aclpb.ACLChange, err error) {
+	aclChange = new(aclpb.ACLChange)
+	err = proto.Unmarshal(change.Payload, aclChange)
+	return
+}
diff --git a/pkg/acl/acltree/treebuilder.go b/pkg/acl/acltree/treebuilder.go
index c8aa9535..261a49f9 100644
--- a/pkg/acl/acltree/treebuilder.go
+++ b/pkg/acl/acltree/treebuilder.go
@@ -135,13 +135,16 @@ func (tb *treeBuilder) buildTree(heads []string, breakpoint string) (err error)
 		return
 	}
 	tb.tree.AddFast(ch)
-	changes, err := tb.dfs(heads, breakpoint)
+	changes, err := tb.dfs(heads, breakpoint, tb.loadChange)
 
 	tb.tree.AddFast(changes...)
 	return
 }
 
-func (tb *treeBuilder) dfs(heads []string, breakpoint string) (buf []*Change, err error) {
+func (tb *treeBuilder) dfs(
+	heads []string,
+	breakpoint string,
+	load func(string) (*Change, error)) (buf []*Change, err error) {
 	stack := make([]string, len(heads), len(heads)*2)
 	copy(stack, heads)
 
@@ -154,7 +157,7 @@ func (tb *treeBuilder) dfs(heads []string, breakpoint string) (buf []*Change, er
 			continue
 		}
 
-		ch, err := tb.loadChange(id)
+		ch, err := load(id)
 		if err != nil {
 			continue
 		}
diff --git a/pkg/acl/example/plaintextdocument/document.go b/pkg/acl/example/plaintextdocument/document.go
index 80e760b0..b25b2f8e 100644
--- a/pkg/acl/example/plaintextdocument/document.go
+++ b/pkg/acl/example/plaintextdocument/document.go
@@ -17,6 +17,7 @@ type PlainTextDocument interface {
 	AddText(ctx context.Context, text string) error
 }
 
+// TODO: this struct is not thread-safe, so use it wisely :-)
 type plainTextDocument struct {
 	heads   []string
 	aclTree acltree.ACLTree
diff --git a/pkg/acl/treestorage/inmemory.go b/pkg/acl/treestorage/inmemory.go
index 8a2b7865..b9015116 100644
--- a/pkg/acl/treestorage/inmemory.go
+++ b/pkg/acl/treestorage/inmemory.go
@@ -143,7 +143,7 @@ func (i *inMemoryTreeStorageProvider) TreeStorage(treeId string) (TreeStorage, e
 	if tree, exists := i.trees[treeId]; exists {
 		return tree, nil
 	}
-	return nil, UnknownTreeId
+	return nil, ErrUnknownTreeId
 }
 
 func (i *inMemoryTreeStorageProvider) InsertTree(tree TreeStorage) error {
diff --git a/pkg/acl/treestorage/provider.go b/pkg/acl/treestorage/provider.go
index c62096db..fd442655 100644
--- a/pkg/acl/treestorage/provider.go
+++ b/pkg/acl/treestorage/provider.go
@@ -2,7 +2,7 @@ package treestorage
 
 import "errors"
 
-var UnknownTreeId = errors.New("tree does not exist")
+var ErrUnknownTreeId = errors.New("tree does not exist")
 
 type Provider interface {
 	TreeStorage(treeId string) (TreeStorage, error)
diff --git a/service/sync/pubsub.go b/service/sync/pubsub.go
deleted file mode 100644
index b85c8e65..00000000
--- a/service/sync/pubsub.go
+++ /dev/null
@@ -1,13 +0,0 @@
-package sync
-
-type PubSubPayload struct {
-}
-
-type PubSub interface {
-	Send(msg *PubSubPayload) error
-	Listen(chan *PubSubPayload) error
-}
-
-func NewPubSub(topic string) PubSub {
-	return nil
-}
diff --git a/service/sync/requesthandler.go b/service/sync/requesthandler.go
index b4d0758b..349f59d3 100644
--- a/service/sync/requesthandler.go
+++ b/service/sync/requesthandler.go
@@ -20,7 +20,7 @@ func (r *requestHander) HandleHeadUpdate(ctx context.Context, senderId string, u
 		snapshotPath []string
 		result       acltree.AddResult
 	)
-	
+
 	err = r.treeCache.Do(ctx, update.TreeId, func(tree acltree.ACLTree) error {
 		// TODO: check if we already have those changes
 		result, err = tree.AddRawChanges(ctx, update.Changes...)
@@ -30,7 +30,7 @@ func (r *requestHander) HandleHeadUpdate(ctx context.Context, senderId string, u
 		shouldFullSync := !slice.UnsortedEquals(update.Heads, tree.Heads())
 		snapshotPath = tree.SnapshotPath()
 		if shouldFullSync {
-			fullRequest, err = r.prepareFullSyncRequest(tree)
+			fullRequest, err = r.prepareFullSyncRequest(update.TreeId, update.SnapshotPath, tree)
 			if err != nil {
 				return err
 			}
@@ -38,7 +38,7 @@ func (r *requestHander) HandleHeadUpdate(ctx context.Context, senderId string, u
 		return nil
 	})
 	// if there are no such tree
-	if err == treestorage.UnknownTreeId {
+	if err == treestorage.ErrUnknownTreeId {
 		fullRequest = &syncpb.SyncFullRequest{
 			TreeId: update.TreeId,
 		}
@@ -62,12 +62,25 @@ func (r *requestHander) HandleHeadUpdate(ctx context.Context, senderId string, u
 	return
 }
 
-func (r *requestHander) HandleFullSync(ctx context.Context, senderId string, request *syncpb.SyncFullRequest) error {
+func (r *requestHander) HandleFullSyncRequest(ctx context.Context, senderId string, request *syncpb.SyncFullRequest) error {
 	// TODO: add case of new tree
 	return nil
 }
 
-func (r *requestHander) prepareFullSyncRequest(tree acltree.ACLTree) (*syncpb.SyncFullRequest, error) {
-
-	return nil, nil
+func (r *requestHander) HandleFullSyncResponse(ctx context.Context, senderId string, request *syncpb.SyncFullRequest) error {
+	// TODO: add case of new tree
+	return nil
+}
+
+func (r *requestHander) prepareFullSyncRequest(treeId string, theirPath []string, tree acltree.ACLTree) (*syncpb.SyncFullRequest, error) {
+	ourChanges, err := tree.ChangesAfterCommonSnapshot(theirPath)
+	if err != nil {
+		return nil, err
+	}
+	return &syncpb.SyncFullRequest{
+		Heads:        tree.Heads(),
+		Changes:      ourChanges,
+		TreeId:       treeId,
+		SnapshotPath: tree.SnapshotPath(),
+	}, nil
 }
diff --git a/service/sync/service.go b/service/sync/service.go
index e26d54eb..fd6839bb 100644
--- a/service/sync/service.go
+++ b/service/sync/service.go
@@ -6,7 +6,6 @@ import (
 )
 
 type service struct {
-	pubSub PubSub
 }
 
 const CName = "SyncService"
diff --git a/service/treecache/service.go b/service/treecache/service.go
index 0aef289c..654d12ca 100644
--- a/service/treecache/service.go
+++ b/service/treecache/service.go
@@ -31,6 +31,9 @@ func (s *service) Do(ctx context.Context, treeId string, f func(tree acltree.ACL
 	if err != nil {
 		return err
 	}
+	aclTree := tree.(acltree.ACLTree)
+	aclTree.Lock()
+	defer aclTree.Unlock()
 	return f(tree.(acltree.ACLTree))
 }