diff --git a/dot/state/block.go b/dot/state/block.go
index 690f4fcdd5..d57df0beb0 100644
--- a/dot/state/block.go
+++ b/dot/state/block.go
@@ -19,7 +19,6 @@ import (
 	"github.com/ChainSafe/gossamer/pkg/scale"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promauto"
-	"golang.org/x/exp/slices"
 
 	rtstorage "github.com/ChainSafe/gossamer/lib/runtime/storage"
 	wazero_runtime "github.com/ChainSafe/gossamer/lib/runtime/wazero"
@@ -255,19 +254,20 @@ func (bs *BlockState) GetHashByNumber(num uint) (common.Hash, error) {
 
 // GetHashesByNumber returns the block hashes with the given number
 func (bs *BlockState) GetHashesByNumber(blockNumber uint) ([]common.Hash, error) {
-	block, err := bs.GetBlockByNumber(blockNumber)
-	if err != nil {
-		return nil, fmt.Errorf("getting block by number: %w", err)
-	}
-
-	blockHashes := bs.bt.GetAllBlocksAtNumber(block.Header.ParentHash)
+	inMemoryBlockHashes := bs.bt.GetHashesAtNumber(blockNumber)
+	if len(inMemoryBlockHashes) == 0 {
+		bh, err := bs.db.Get(headerHashKey(uint64(blockNumber)))
+		if err != nil {
+			if errors.Is(err, database.ErrNotFound) {
+				return []common.Hash{}, nil
+			}
+			return []common.Hash{}, fmt.Errorf("cannot get block by its number %d: %w", blockNumber, err)
+		}
 
-	hash := block.Header.Hash()
-	if !slices.Contains(blockHashes, hash) {
-		blockHashes = append(blockHashes, hash)
+		return []common.Hash{common.NewHash(bh)}, nil
 	}
 
-	return blockHashes, nil
+	return inMemoryBlockHashes, nil
 }
 
 // GetAllDescendants gets all the descendants for a given block hash (including itself), by first checking in memory
@@ -496,17 +496,7 @@ func (bs *BlockState) AddBlockWithArrivalTime(block *types.Block, arrivalTime ti
 
 // GetAllBlocksAtNumber returns all unfinalised blocks with the given number
 func (bs *BlockState) GetAllBlocksAtNumber(num uint) ([]common.Hash, error) {
-	header, err := bs.GetHeaderByNumber(num)
-	if err != nil {
-		return nil, err
-	}
-
-	return bs.GetAllBlocksAtDepth(header.ParentHash), nil
-}
-
-// GetAllBlocksAtDepth returns all hashes with the depth of the given hash plus one
-func (bs *BlockState) GetAllBlocksAtDepth(hash common.Hash) []common.Hash {
-	return bs.bt.GetAllBlocksAtNumber(hash)
+	return bs.bt.GetHashesAtNumber(num), nil
 }
 
 func (bs *BlockState) isBlockOnCurrentChain(header *types.Header) (bool, error) {
diff --git a/dot/state/grandpa_test.go b/dot/state/grandpa_test.go
index 8018308c0b..7043cac47b 100644
--- a/dot/state/grandpa_test.go
+++ b/dot/state/grandpa_test.go
@@ -143,7 +143,7 @@ func testBlockState(t *testing.T, db database.Database) *BlockState {
 	return bs
 }
 
-func TestAddScheduledChangesKeepTheRightForkTree(t *testing.T) {
+func TestAddScheduledChangesKeepTheRightForkTree(t *testing.T) { //nolint:tparallel
 	t.Parallel()
 
 	keyring, err := keystore.NewSr25519Keyring()
@@ -220,8 +220,6 @@ func TestAddScheduledChangesKeepTheRightForkTree(t *testing.T) {
 	for tname, tt := range tests {
 		tt := tt
 		t.Run(tname, func(t *testing.T) {
-			t.Parallel()
-
 			// clear the scheduledChangeRoots after the test ends
 			// this does not cause race condition because t.Run without
 			// t.Parallel() blocks until this function returns
diff --git a/lib/babe/mock_state_test.go b/lib/babe/mock_state_test.go
index c9b3b83da2..ab5e132028 100644
--- a/lib/babe/mock_state_test.go
+++ b/lib/babe/mock_state_test.go
@@ -113,20 +113,6 @@ func (mr *MockBlockStateMockRecorder) GenesisHash() *gomock.Call {
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GenesisHash", reflect.TypeOf((*MockBlockState)(nil).GenesisHash))
 }
 
-// GetAllBlocksAtDepth mocks base method.
-func (m *MockBlockState) GetAllBlocksAtDepth(arg0 common.Hash) []common.Hash {
-	m.ctrl.T.Helper()
-	ret := m.ctrl.Call(m, "GetAllBlocksAtDepth", arg0)
-	ret0, _ := ret[0].([]common.Hash)
-	return ret0
-}
-
-// GetAllBlocksAtDepth indicates an expected call of GetAllBlocksAtDepth.
-func (mr *MockBlockStateMockRecorder) GetAllBlocksAtDepth(arg0 any) *gomock.Call {
-	mr.mock.ctrl.T.Helper()
-	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetAllBlocksAtDepth", reflect.TypeOf((*MockBlockState)(nil).GetAllBlocksAtDepth), arg0)
-}
-
 // GetBlockByNumber mocks base method.
 func (m *MockBlockState) GetBlockByNumber(arg0 uint) (*types.Block, error) {
 	m.ctrl.T.Helper()
diff --git a/lib/babe/state.go b/lib/babe/state.go
index 47de36a930..f4aee6f4d4 100644
--- a/lib/babe/state.go
+++ b/lib/babe/state.go
@@ -24,7 +24,6 @@ type BlockState interface {
 	BestBlockHash() common.Hash
 	BestBlockHeader() (*types.Header, error)
 	AddBlock(*types.Block) error
-	GetAllBlocksAtDepth(hash common.Hash) []common.Hash
 	GetHeader(common.Hash) (*types.Header, error)
 	GetBlockByNumber(blockNumber uint) (*types.Block, error)
 	GetBlockHashesBySlot(slot uint64) (blockHashes []common.Hash, err error)
diff --git a/lib/blocktree/blocktree.go b/lib/blocktree/blocktree.go
index 0f1faf21cc..0fa4e4d06e 100644
--- a/lib/blocktree/blocktree.go
+++ b/lib/blocktree/blocktree.go
@@ -120,24 +120,24 @@ func (bt *BlockTree) AddBlock(header *types.Header, arrivalTime time.Time) (err
 	return nil
 }
 
-// GetAllBlocksAtNumber will return all blocks hashes with the number of the given hash plus one.
+// GetHashesAtNumber will return all blocks hashes that contains the number of the given hash plus one.
 // To find all blocks at a number matching a certain block, pass in that block's parent hash
-func (bt *BlockTree) GetAllBlocksAtNumber(hash common.Hash) (hashes []common.Hash) {
+func (bt *BlockTree) GetHashesAtNumber(number uint) (hashes []common.Hash) {
 	bt.RLock()
 	defer bt.RUnlock()
 
-	if bt.getNode(hash) == nil {
-		return hashes
+	if number < bt.root.number {
+		return []common.Hash{}
 	}
 
-	number := bt.getNode(hash).number + 1
-
-	if bt.root.number == number {
-		hashes = append(hashes, bt.root.hash)
-		return hashes
+	bestLeave := bt.leaves.bestBlock()
+	if number > bestLeave.number {
+		return []common.Hash{}
 	}
 
-	return bt.root.getNodesWithNumber(number, hashes)
+	possibleNumOfBlocks := len(bt.leaves.nodes())
+	hashes = make([]common.Hash, 0, possibleNumOfBlocks)
+	return bt.root.hashesAtNumber(number, hashes)
 }
 
 var ErrStartGreaterThanEnd = errors.New("start greater than end")
diff --git a/lib/blocktree/blocktree_test.go b/lib/blocktree/blocktree_test.go
index f7833eeec5..bca3a93e16 100644
--- a/lib/blocktree/blocktree_test.go
+++ b/lib/blocktree/blocktree_test.go
@@ -139,9 +139,10 @@ func Test_BlockTree_GetNode(t *testing.T) {
 	require.NotNil(t, block)
 }
 
-func Test_BlockTree_GetAllBlocksAtNumber(t *testing.T) {
+func Test_BlockTree_GetHashesAtNumber(t *testing.T) {
 	bt, _ := createTestBlockTree(t, testHeader, 8)
-	hashes := bt.root.getNodesWithNumber(10, []common.Hash{})
+	hashes := make([]common.Hash, 0)
+	hashes = bt.root.hashesAtNumber(10, hashes)
 
 	require.Empty(t, hashes)
 
@@ -194,7 +195,8 @@ func Test_BlockTree_GetAllBlocksAtNumber(t *testing.T) {
 		}
 	}
 
-	hashes = bt.root.getNodesWithNumber(desiredNumber, []common.Hash{})
+	hashes = make([]common.Hash, 0, 100)
+	hashes = bt.root.hashesAtNumber(desiredNumber, hashes)
 	require.Equal(t, expected, hashes)
 }
 
diff --git a/lib/blocktree/node.go b/lib/blocktree/node.go
index 557f805066..5eb4556860 100644
--- a/lib/blocktree/node.go
+++ b/lib/blocktree/node.go
@@ -59,20 +59,23 @@ func (n *node) getNode(h common.Hash) *node {
 	return nil
 }
 
-// getNodesWithNumber returns all descendent nodes with the desired number
-func (n *node) getNodesWithNumber(number uint, hashes []common.Hash) []common.Hash {
-	for _, child := range n.children {
-		// number matches
-		if child.number == number {
-			hashes = append(hashes, child.hash)
-		}
-
-		// are deeper than desired number, return
-		if child.number > number {
-			return hashes
+// hashesAtNumber returns all nodes in the chain that contains the desired number
+func (n *node) hashesAtNumber(number uint, hashes []common.Hash) []common.Hash {
+	// there is no need to go furthen in the node's children
+	// since they have a greater number at least
+	if number == n.number {
+		hashes = append(hashes, n.hash)
+		return hashes
+	}
+
+	// if the number is greater than current node,
+	// then search among its children
+	if number > n.number {
+		for _, children := range n.children {
+			hashes = children.hashesAtNumber(number, hashes)
 		}
 
-		hashes = child.getNodesWithNumber(number, hashes)
+		return hashes
 	}
 
 	return hashes