diff --git a/src/db/db/dbCell.cc b/src/db/db/dbCell.cc
index bda9d71f8..e8d2a1c9f 100644
--- a/src/db/db/dbCell.cc
+++ b/src/db/db/dbCell.cc
@@ -93,7 +93,7 @@ Cell::box_type Cell::ms_empty_box = Cell::box_type ();
 Cell::Cell (cell_index_type ci, db::Layout &l) 
   : db::Object (l.manager ()), 
     m_cell_index (ci), mp_layout (&l), m_instances (this), m_prop_id (0), m_hier_levels (0),
-    m_instances_need_sort (false), m_instances_need_sort_box_tree (false), m_bbox_needs_update (false), m_ghost_cell (false),
+    m_bbox_needs_update (false), m_ghost_cell (false),
     mp_last (0), mp_next (0)
 {
   //  .. nothing yet 
@@ -132,10 +132,6 @@ Cell::operator= (const Cell &d)
     m_prop_id = d.m_prop_id;
     m_bbox_needs_update = d.m_bbox_needs_update;
 
-    //  need to update the instances inst_by_cell_index pointers
-    m_instances_need_sort = true;
-    m_instances_need_sort_box_tree = true;
-
   }
   return *this;
 }
@@ -618,8 +614,6 @@ Cell::invalidate_insts ()
 {
   mp_layout->invalidate_hier ();  //  HINT: must come before the change is done!
   mp_layout->invalidate_bboxes (std::numeric_limits<unsigned int>::max ());
-  m_instances_need_sort = true;
-  m_instances_need_sort_box_tree = true;
   m_bbox_needs_update = true;
 }
 
@@ -707,10 +701,7 @@ Cell::clear_parent_insts (size_t sz)
 void 
 Cell::sort_child_insts ()
 {
-  if (m_instances_need_sort) {
-    m_instances.sort_child_insts ();
-  }
-  m_instances_need_sort = false;
+  m_instances.sort_child_insts ();
 }
 
 std::pair<bool, db::pcell_id_type> 
@@ -756,10 +747,7 @@ Cell::change_pcell_parameters (const instance_type &ref, const std::vector<tl::V
 void 
 Cell::sort_inst_tree (bool force)
 {
-  if (force || m_instances_need_sort_box_tree) {
-    m_instances.sort_inst_tree (mp_layout);
-  }
-  m_instances_need_sort_box_tree = false;
+  m_instances.sort_inst_tree (mp_layout, force);
 
   //  update the number of hierarchy levels
   m_hier_levels = count_hier_levels ();
diff --git a/src/db/db/dbCell.h b/src/db/db/dbCell.h
index 162b7fe49..0d74ae1ab 100644
--- a/src/db/db/dbCell.h
+++ b/src/db/db/dbCell.h
@@ -1076,9 +1076,7 @@ private:
   db::properties_id_type m_prop_id;
 
   // packed fields
-  unsigned int m_hier_levels : 28;
-  bool m_instances_need_sort : 1;
-  bool m_instances_need_sort_box_tree : 1;
+  unsigned int m_hier_levels : 30;
   bool m_bbox_needs_update : 1;
   bool m_ghost_cell : 1;
 
diff --git a/src/db/db/dbInstances.cc b/src/db/db/dbInstances.cc
index 22248152a..c0a0f4ca3 100644
--- a/src/db/db/dbInstances.cc
+++ b/src/db/db/dbInstances.cc
@@ -940,6 +940,9 @@ Instances::operator= (const Instances &d)
 
     m_parent_insts = d.m_parent_insts;
 
+    set_instance_by_cell_index_needs_made (true);
+    set_instance_tree_needs_sort (true);
+
   }
   return *this;
 }
@@ -947,13 +950,24 @@ Instances::operator= (const Instances &d)
 bool 
 Instances::is_editable () const
 {
-  return mp_cell && mp_cell->layout () ? mp_cell->layout ()->is_editable () : true;
+  return cell () && cell ()->layout () ? cell ()->layout ()->is_editable () : true;
 }
 
 db::Layout *
 Instances::layout () const
 {
-  return mp_cell ? mp_cell->layout () : 0;
+  return cell () ? cell ()->layout () : 0;
+}
+
+void
+Instances::invalidate_insts ()
+{
+  if (cell ()) {
+    cell ()->invalidate_insts ();
+  }
+
+  set_instance_by_cell_index_needs_made (true);
+  set_instance_tree_needs_sort (true);
 }
 
 template <class Tag, class ET, class I>
@@ -962,14 +976,15 @@ Instances::erase_positions (Tag tag, ET editable_tag, I first, I last)
 {
   typedef instances_editable_traits<ET> editable_traits;
 
-  if (mp_cell) { 
-    mp_cell->invalidate_insts ();  //  HINT: must come before the change is done!
-    if (mp_cell->manager () && mp_cell->manager ()->transacting ()) {
+  invalidate_insts ();  //  HINT: must come before the change is done!
+
+  if (cell ()) {
+    if (cell ()->manager () && cell ()->manager ()->transacting ()) {
       check_is_editable_for_undo_redo (this);
       if (! is_editable ()) {
         throw tl::Exception (tl::to_string (tr ("No undo/redo support for non-editable instance lists in 'erase_positions'")));
       }
-      mp_cell->manager ()->queue (mp_cell, new db::InstOp<typename Tag::object_type, ET> (false /*not insert*/, first, last, true /*dummy*/));
+      cell ()->manager ()->queue (cell (), new db::InstOp<typename Tag::object_type, ET> (false /*not insert*/, first, last, true /*dummy*/));
     }
   }
 
@@ -983,18 +998,19 @@ Instances::insert (const InstArray &inst)
 {
   bool editable = is_editable ();
 
-  if (mp_cell) {
-    if (mp_cell->manager () && mp_cell->manager ()->transacting ()) {
+  if (cell ()) {
+    if (cell ()->manager () && cell ()->manager ()->transacting ()) {
       check_is_editable_for_undo_redo (this);
       if (editable) {
-        mp_cell->manager ()->queue (mp_cell, new db::InstOp<InstArray, InstancesEditableTag> (true /*insert*/, inst));
+        cell ()->manager ()->queue (cell (), new db::InstOp<InstArray, InstancesEditableTag> (true /*insert*/, inst));
       } else {
-        mp_cell->manager ()->queue (mp_cell, new db::InstOp<InstArray, InstancesNonEditableTag> (true /*insert*/, inst));
+        cell ()->manager ()->queue (cell (), new db::InstOp<InstArray, InstancesNonEditableTag> (true /*insert*/, inst));
       }
     }
-    mp_cell->invalidate_insts ();
   }
 
+  invalidate_insts ();
+
   // TODO: simplify this, i.e. through instance_from_pointer
   if (editable) {
     return instance_type (this, inst_tree (typename InstArray::tag (), InstancesEditableTag ()).insert (inst));
@@ -1010,14 +1026,14 @@ Instances::insert (I from, I to)
   typedef std::iterator_traits<I> it_traits;
   typedef typename it_traits::value_type value_type;
 
-  if (mp_cell) {
-    if (mp_cell->manager () && mp_cell->manager ()->transacting ()) {
+  if (cell ()) {
+    if (cell ()->manager () && cell ()->manager ()->transacting ()) {
       check_is_editable_for_undo_redo (this);
-      mp_cell->manager ()->queue (mp_cell, new db::InstOp<typename it_traits::value_type, ET> (true /*insert*/, from, to));
+      cell ()->manager ()->queue (cell (), new db::InstOp<typename it_traits::value_type, ET> (true /*insert*/, from, to));
     }
-    mp_cell->invalidate_insts ();
   }
 
+  invalidate_insts ();
   inst_tree (typename value_type::tag (), ET ()).insert (from, to);
 }
 
@@ -1061,20 +1077,21 @@ template <class InstArray>
 void 
 Instances::replace (const InstArray *replace, const InstArray &with)
 {
-  if (mp_cell) {
-    if (mp_cell->manager () && mp_cell->manager ()->transacting ()) {
+  if (cell ()) {
+    if (cell ()->manager () && cell ()->manager ()->transacting ()) {
       check_is_editable_for_undo_redo (this);
       if (is_editable ()) {
-        mp_cell->manager ()->queue (mp_cell, new db::InstOp<InstArray, InstancesEditableTag> (false /*not insert*/, *replace));
-        mp_cell->manager ()->queue (mp_cell, new db::InstOp<InstArray, InstancesEditableTag> (true /*insert*/, with));
+        cell ()->manager ()->queue (cell (), new db::InstOp<InstArray, InstancesEditableTag> (false /*not insert*/, *replace));
+        cell ()->manager ()->queue (cell (), new db::InstOp<InstArray, InstancesEditableTag> (true /*insert*/, with));
       } else {
-        mp_cell->manager ()->queue (mp_cell, new db::InstOp<InstArray, InstancesNonEditableTag> (false /*not insert*/, *replace));
-        mp_cell->manager ()->queue (mp_cell, new db::InstOp<InstArray, InstancesNonEditableTag> (true /*insert*/, with));
+        cell ()->manager ()->queue (cell (), new db::InstOp<InstArray, InstancesNonEditableTag> (false /*not insert*/, *replace));
+        cell ()->manager ()->queue (cell (), new db::InstOp<InstArray, InstancesNonEditableTag> (true /*insert*/, with));
       }
     }
-    mp_cell->invalidate_insts ();
   }
 
+  invalidate_insts ();
+
   //  HINT: this only works because we know our box trees well:
   *((InstArray *)replace) = with;
 }
@@ -1150,11 +1167,12 @@ Instances::erase_inst_by_iter (Tag tag, ET editable_tag, I iter)
     throw tl::Exception (tl::to_string (tr ("Trying to erase an object from a list that it does not belong to")));
   }
 
-  if (mp_cell) {
-    mp_cell->invalidate_insts ();
-    if (mp_cell->manager () && mp_cell->manager ()->transacting ()) {
+  invalidate_insts ();
+
+  if (cell ()) {
+    if (cell ()->manager () && cell ()->manager ()->transacting ()) {
       check_is_editable_for_undo_redo (this);
-      mp_cell->manager ()->queue (mp_cell, new db::InstOp<typename Tag::object_type, ET> (false /*not insert*/, *iter));
+      cell ()->manager ()->queue (cell (), new db::InstOp<typename Tag::object_type, ET> (false /*not insert*/, *iter));
     }
   }
 
@@ -1165,11 +1183,12 @@ template <class Tag, class ET>
 void 
 Instances::erase_inst_by_tag (Tag tag, ET editable_tag, const typename Tag::object_type &obj)
 {
-  if (mp_cell) {
-    mp_cell->invalidate_insts ();
-    if (mp_cell->manager () && mp_cell->manager ()->transacting ()) {
+  invalidate_insts ();
+
+  if (cell ()) {
+    if (cell ()->manager () && cell ()->manager ()->transacting ()) {
       check_is_editable_for_undo_redo (this);
-      mp_cell->manager ()->queue (mp_cell, new db::InstOp<typename Tag::object_type, ET> (false /*not insert*/, obj));
+      cell ()->manager ()->queue (cell (), new db::InstOp<typename Tag::object_type, ET> (false /*not insert*/, obj));
     }
   }
 
@@ -1197,16 +1216,17 @@ template <class ET>
 void
 Instances::clear_insts (ET editable_tag)
 {
-  if (mp_cell) {
-    mp_cell->invalidate_insts ();
-    if (mp_cell->manager () && mp_cell->manager ()->transacting ()) {
+  invalidate_insts ();
+
+  if (cell ()) {
+    if (cell ()->manager () && cell ()->manager ()->transacting ()) {
       check_is_editable_for_undo_redo (this);
       const Instances *const_this = this;
       if (! const_this->inst_tree (cell_inst_array_type::tag (), editable_tag).empty ()) {
-        mp_cell->manager ()->queue (mp_cell, new db::InstOp<cell_inst_array_type, ET> (false /*not insert*/, const_this->inst_tree (cell_inst_array_type::tag (), editable_tag).begin (), const_this->inst_tree (cell_inst_array_type::tag (), editable_tag).end ()));
+        cell ()->manager ()->queue (cell (), new db::InstOp<cell_inst_array_type, ET> (false /*not insert*/, const_this->inst_tree (cell_inst_array_type::tag (), editable_tag).begin (), const_this->inst_tree (cell_inst_array_type::tag (), editable_tag).end ()));
       }
       if (! const_this->inst_tree (cell_inst_wp_array_type::tag (), editable_tag).empty ()) {
-        mp_cell->manager ()->queue (mp_cell, new db::InstOp<cell_inst_wp_array_type, ET> (false /*not insert*/, const_this->inst_tree (cell_inst_wp_array_type::tag (), editable_tag).begin (), const_this->inst_tree (cell_inst_wp_array_type::tag (), editable_tag).end ()));
+        cell ()->manager ()->queue (cell (), new db::InstOp<cell_inst_wp_array_type, ET> (false /*not insert*/, const_this->inst_tree (cell_inst_wp_array_type::tag (), editable_tag).begin (), const_this->inst_tree (cell_inst_wp_array_type::tag (), editable_tag).end ()));
       }
     }
   }
@@ -1227,9 +1247,7 @@ Instances::clear_insts ()
 void 
 Instances::clear (Instances::cell_inst_array_type::tag) 
 {
-  if (mp_cell) {
-    mp_cell->invalidate_insts ();
-  }
+  invalidate_insts ();
 
   if (m_generic.any) {
     if (is_editable ()) {
@@ -1244,9 +1262,7 @@ Instances::clear (Instances::cell_inst_array_type::tag)
 void 
 Instances::clear (Instances::cell_inst_wp_array_type::tag) 
 {
-  if (mp_cell) {
-    mp_cell->invalidate_insts ();
-  }
+  invalidate_insts ();
 
   if (m_generic_wp.any) {
     if (is_editable ()) {
@@ -1373,6 +1389,11 @@ struct cell_inst_compare_f
 void 
 Instances::sort_child_insts () 
 {
+  if (! instance_by_cell_index_needs_made ()) {
+    return;
+  }
+  set_instance_by_cell_index_needs_made (false);
+
   m_insts_by_cell_index = sorted_inst_vector ();
   m_insts_by_cell_index.reserve (cell_instances ());
 
@@ -1406,8 +1427,13 @@ Instances::sort_child_insts ()
 }
 
 void 
-Instances::sort_inst_tree (const Layout *g)
+Instances::sort_inst_tree (const Layout *g, bool force)
 {
+  if (! force && ! instance_tree_needs_sort ()) {
+    return;
+  }
+  set_instance_tree_needs_sort (false);
+
   if (m_generic.any) {
     if (is_editable ()) {
       m_generic.stable_tree->sort (cell_inst_array_box_converter (*g));
@@ -1603,16 +1629,17 @@ void Instances::apply_op (const Op &op, ET editable_tag)
   bool has_insts = ! const_this->inst_tree (cell_inst_array_type::tag (), editable_tag).empty ();
   bool has_wp_insts = ! const_this->inst_tree (cell_inst_wp_array_type::tag (), editable_tag).empty ();
 
-  if (mp_cell) {
-    mp_cell->invalidate_insts ();
-    if (mp_cell->manager () && mp_cell->manager ()->transacting ()) {
+  invalidate_insts ();
+
+  if (cell ()) {
+    if (cell ()->manager () && cell ()->manager ()->transacting ()) {
       check_is_editable_for_undo_redo (this);
       transacting = true;
       if (has_insts) {
-        mp_cell->manager ()->queue (mp_cell, new db::InstOp<cell_inst_array_type, ET> (false /*not insert*/, const_this->inst_tree (cell_inst_array_type::tag (), editable_tag).begin (), const_this->inst_tree (cell_inst_array_type::tag (), editable_tag).end ()));
+        cell ()->manager ()->queue (cell (), new db::InstOp<cell_inst_array_type, ET> (false /*not insert*/, const_this->inst_tree (cell_inst_array_type::tag (), editable_tag).begin (), const_this->inst_tree (cell_inst_array_type::tag (), editable_tag).end ()));
       }
       if (has_wp_insts) {
-        mp_cell->manager ()->queue (mp_cell, new db::InstOp<cell_inst_wp_array_type, ET> (false /*not insert*/, const_this->inst_tree (cell_inst_wp_array_type::tag (), editable_tag).begin (), const_this->inst_tree (cell_inst_wp_array_type::tag (), editable_tag).end ()));
+        cell ()->manager ()->queue (cell (), new db::InstOp<cell_inst_wp_array_type, ET> (false /*not insert*/, const_this->inst_tree (cell_inst_wp_array_type::tag (), editable_tag).begin (), const_this->inst_tree (cell_inst_wp_array_type::tag (), editable_tag).end ()));
       }
     }
   }
@@ -1637,10 +1664,10 @@ void Instances::apply_op (const Op &op, ET editable_tag)
 
   if (transacting) {
     if (has_insts) {
-      mp_cell->manager ()->queue (mp_cell, new db::InstOp<cell_inst_array_type, ET> (true /*insert*/, const_this->inst_tree (cell_inst_array_type::tag (), editable_tag).begin (), const_this->inst_tree (cell_inst_array_type::tag (), editable_tag).end ()));
+      cell ()->manager ()->queue (cell (), new db::InstOp<cell_inst_array_type, ET> (true /*insert*/, const_this->inst_tree (cell_inst_array_type::tag (), editable_tag).begin (), const_this->inst_tree (cell_inst_array_type::tag (), editable_tag).end ()));
     }
     if (has_wp_insts) {
-      mp_cell->manager ()->queue (mp_cell, new db::InstOp<cell_inst_wp_array_type, ET> (true /*insert*/, const_this->inst_tree (cell_inst_wp_array_type::tag (), editable_tag).begin (), const_this->inst_tree (cell_inst_wp_array_type::tag (), editable_tag).end ()));
+      cell ()->manager ()->queue (cell (), new db::InstOp<cell_inst_wp_array_type, ET> (true /*insert*/, const_this->inst_tree (cell_inst_wp_array_type::tag (), editable_tag).begin (), const_this->inst_tree (cell_inst_wp_array_type::tag (), editable_tag).end ()));
     }
   }
 }
diff --git a/src/db/db/dbInstances.h b/src/db/db/dbInstances.h
index 9a7575941..e57b64eac 100644
--- a/src/db/db/dbInstances.h
+++ b/src/db/db/dbInstances.h
@@ -1553,10 +1553,11 @@ public:
   /**
    *  @brief Sort the cell instance list
    *
-   *  This will sort the cell instance list. As a prerequesite
+   *  This will sort the cell instance list (quad tree sort). As a prerequesite
    *  the cell's bounding boxes must have been computed.
+   *  If force is true, the instance tree is always sorted.
    */
-  void sort_inst_tree (const layout_type *g);
+  void sort_inst_tree (const layout_type *g, bool force);
 
   /**
    *  @brief Update the child-parent relationships
@@ -1701,14 +1702,6 @@ public:
     return m_parent_insts.end () == m_parent_insts.begin ();
   }
 
-  /**
-   *  @brief Gets the cell pointer the instance container is in
-   */
-  db::Cell *cell () const
-  {
-    return mp_cell;
-  }
-
   /**
    *  @brief Gets the layout the instances collection lives in
    */
@@ -1724,6 +1717,14 @@ public:
    */
   bool is_editable () const;
 
+  /**
+   *  @brief Gets the cell pointer
+   */
+  cell_type *cell () const
+  {
+    return reinterpret_cast<cell_type *> (size_t (mp_cell) & ~size_t (3));
+  }
+
   /**
    *  @brief Delegate for the undo method
    */
@@ -1735,6 +1736,7 @@ public:
   void redo (db::Op *op);
 
 private:
+  friend class Instance;
   friend struct NormalInstanceIteratorTraits;
   friend struct TouchingInstanceIteratorTraits;
   friend struct OverlappingInstanceIteratorTraits;
@@ -1761,6 +1763,43 @@ private:
   static stable_cell_inst_wp_tree_type ms_empty_stable_wp_tree;
   static stable_cell_inst_tree_type ms_empty_stable_tree;
 
+  /**
+   *  @brief Sets a flag indicating that the instance tree needs sorting
+   */
+  void set_instance_tree_needs_sort (bool f)
+  {
+    mp_cell = reinterpret_cast<cell_type *> ((size_t (mp_cell) & ~size_t (1)) | size_t (f ? 1 : 0));
+  }
+
+  /**
+   *  @brief Sets a flag indicating that the instance tree needs sorting
+   */
+  bool instance_tree_needs_sort () const
+  {
+    return (size_t (mp_cell) & 1) != 0;
+  }
+
+  /**
+   *  @brief Sets a flag indicating that the instance by cell index cache needs made
+   */
+  void set_instance_by_cell_index_needs_made (bool f)
+  {
+    mp_cell = reinterpret_cast<cell_type *> ((size_t (mp_cell) & ~size_t (2)) | size_t (f ? 2 : 0));
+  }
+
+  /**
+   *  @brief Sets a flag indicating that the instance tree needs sorting
+   */
+  bool instance_by_cell_index_needs_made () const
+  {
+    return (size_t (mp_cell) & 2) != 0;
+  }
+
+  /**
+   *  @brief Invalidates the instance information - called whenever something changes
+   */
+  void invalidate_insts ();
+
   /**
    *  @brief Get the non-editable instance tree by instance type
    */
diff --git a/src/db/db/dbLayout.cc b/src/db/db/dbLayout.cc
index dc550432c..a02ffa949 100644
--- a/src/db/db/dbLayout.cc
+++ b/src/db/db/dbLayout.cc
@@ -1097,15 +1097,17 @@ Layout::do_prune_cell_or_subcell (cell_index_type id, int levels, bool subcells)
   //  collect the called cells
   std::set <cell_index_type> called;
   cref.collect_called_cells (called, levels);
-  called.insert (id);
+  if (! subcells) {
+    called.insert (id);
+  }
 
   //  From these cells erase all cells that have parents outside the subtree of our cell.
   //  Make sure this is done recursively by doing this top-down.
   for (top_down_iterator c = begin_top_down (); c != end_top_down (); ++c) {
-    if (called.find (*c) != called.end () && *c != id) {
+    if (*c != id && called.find (*c) != called.end ()) {
       db::Cell &ccref = cell (*c);
       for (db::Cell::parent_cell_iterator pc = ccref.begin_parent_cells (); pc != ccref.end_parent_cells (); ++pc) {
-        if (called.find (*pc) == called.end ()) {
+        if (*pc != id && called.find (*pc) == called.end ()) {
           //  we have a parent outside the subset considered currently (either the cell was never in or
           //  it was removed itself already): remove this cell from the set of valid subcells.
           called.erase (*c);
@@ -1115,17 +1117,8 @@ Layout::do_prune_cell_or_subcell (cell_index_type id, int levels, bool subcells)
     }
   }
 
-  //  order the called cells bottom-up 
-  std::vector <cell_index_type> cells_to_delete;
-  cells_to_delete.reserve (called.size ());
-  for (bottom_up_iterator c = begin_bottom_up (); c != end_bottom_up (); ++c) {
-    if (called.find (*c) != called.end () && (!subcells || *c != id)) {
-      cells_to_delete.push_back (*c);
-    }
-  }
-
-  //  and delete these cells
-  delete_cells (cells_to_delete.begin (), cells_to_delete.end ());
+  //  and delete the cells
+  delete_cells (called);
 
   //  erase all instances in the subcells case (because, by definition we don't have any more instances)
   if (subcells) {