diff --git a/lib/ae_mdw/db/sync/block.ex b/lib/ae_mdw/db/sync/block.ex
index db8f95af7..1667b4cc5 100644
--- a/lib/ae_mdw/db/sync/block.ex
+++ b/lib/ae_mdw/db/sync/block.ex
@@ -49,11 +49,11 @@ defmodule AeMdw.Db.Sync.Block do
           Txs.txi(),
           Blocks.height() | Blocks.block_hash()
         ) ::
-          {[height_mutations()], Txs.txi()}
+          Enumerable.t()
   def blocks_mutations(from_height, from_mbi, from_txi, to_height_or_hash) do
     from_height
     |> Db.get_blocks_per_height(to_height_or_hash)
-    |> Enum.flat_map_reduce(from_txi, fn {key_block, micro_blocks, next_kb_hash}, txi ->
+    |> Stream.transform(from_txi, fn {key_block, micro_blocks, next_kb_hash}, txi ->
       height = :aec_blocks.height(key_block)
       kb_header = :aec_blocks.to_key_header(key_block)
       {:ok, kb_hash} = :aec_headers.hash_header(kb_header)
diff --git a/lib/ae_mdw/sync/server.ex b/lib/ae_mdw/sync/server.ex
index 0ec7c9239..876304811 100644
--- a/lib/ae_mdw/sync/server.ex
+++ b/lib/ae_mdw/sync/server.ex
@@ -245,17 +245,14 @@ defmodule AeMdw.Sync.Server do
       end
 
     spawn_task(fn ->
-      {mutations_time, {gens_mutations, _next_txi}} =
-        :timer.tc(fn ->
-          Block.blocks_mutations(from_height, from_mbi, from_txi, to_height)
-        end)
-
-      MutationsCache.clear()
+      gens_mutations = Block.blocks_mutations(from_height, from_mbi, from_txi, to_height)
 
       {exec_time, new_state} =
         :timer.tc(fn -> exec_db_mutations(gens_mutations, db_state, clear_mem?) end)
 
-      gens_per_min = (to_height + 1 - from_height) * 60_000_000 / (mutations_time + exec_time)
+      MutationsCache.clear()
+
+      gens_per_min = (to_height + 1 - from_height) * 60_000_000 / exec_time
       Status.set_gens_per_min(gens_per_min)
 
       new_state
@@ -273,15 +270,8 @@ defmodule AeMdw.Sync.Server do
           :none -> -1
         end
 
-      {mutations_time, {gens_mutations, _next_txi}} =
-        :timer.tc(fn ->
-          Block.blocks_mutations(from_height, from_mbi, from_txi, last_hash)
-        end)
-
-      {exec_time, _new_state} = :timer.tc(fn -> exec_mem_mutations(gens_mutations, mem_state) end)
-
-      gens_per_min = length(gens_mutations) * 60_000_000 / (mutations_time + exec_time)
-      Status.set_gens_per_min(gens_per_min)
+      gens_mutations = Block.blocks_mutations(from_height, from_mbi, from_txi, last_hash)
+      _new_state = exec_mem_mutations(gens_mutations, mem_state)
 
       last_hash
     end)
diff --git a/test/ae_mdw/db/sync/block_test.exs b/test/ae_mdw/db/sync/block_test.exs
index 4c018a536..201ba7b54 100644
--- a/test/ae_mdw/db/sync/block_test.exs
+++ b/test/ae_mdw/db/sync/block_test.exs
@@ -70,8 +70,8 @@ defmodule AeMdw.Db.Sync.BlockTest do
         last_mb_hash = AeMdw.Validate.id!(last_mb_hash)
 
         assert mem1 = :ets.info(:sync_hashes, :memory)
-        assert {height_blocks, txi} = Block.blocks_mutations(0, 0, 0, last_mb_hash)
-        assert {^height_blocks, ^txi} = Block.blocks_mutations(0, 0, 0, last_mb_hash)
+        assert height_blocks = 0 |> Block.blocks_mutations(0, 0, last_mb_hash) |> Enum.to_list()
+        assert ^height_blocks = 0 |> Block.blocks_mutations(0, 0, last_mb_hash) |> Enum.to_list()
         assert length(height_blocks) == 11
         assert mem2 = :ets.info(:sync_hashes, :memory)
         assert mem2 > mem1
diff --git a/test/ae_mdw/sync/block_test.exs b/test/ae_mdw/sync/block_test.exs
deleted file mode 100644
index 1c990cf5b..000000000
--- a/test/ae_mdw/sync/block_test.exs
+++ /dev/null
@@ -1,81 +0,0 @@
-defmodule AeMdw.Sync.BlockTest do
-  use ExUnit.Case
-
-  alias AeMdw.Db.Model
-  alias AeMdw.Db.Sync.Block
-
-  import AeMdwWeb.BlockchainSim,
-    only: [with_blockchain: 3, tx: 3, spend_tx: 3, name_tx: 3, name_tx: 4]
-
-  import Mock
-
-  require Model
-
-  describe "blocks_mutations/4" do
-    test "returns the mutations for a generation with many transactions" do
-      # credo:disable-for-next-line
-      accounts = Map.new(0..100, fn i -> {String.to_atom("user#{i}"), 100_000_000} end)
-
-      first_microblock = {
-        :mb0,
-        List.flatten(
-          Enum.map(1..30, fn i ->
-            # credo:disable-for-next-line
-            tx_tag = String.to_atom("tx#{i}")
-            user = String.to_existing_atom("user#{i}")
-            name = "name#{i}.chain"
-            {tx_tag, name_tx(:name_claim_tx, user, name)}
-          end) ++
-            Enum.map(31..40, fn i ->
-              # credo:disable-for-next-line
-              tx_tag = String.to_atom("tx#{i}")
-              user = String.to_existing_atom("user#{i}")
-              {tx_tag, tx(:oracle_register_tx, user, %{})}
-            end) ++
-            Enum.map(41..100, fn i ->
-              # credo:disable-for-next-line
-              tx_tag = String.to_atom("tx#{i}")
-              user = String.to_existing_atom("user#{i}")
-              {tx_tag, spend_tx(user, user, 1_000)}
-            end)
-        )
-      }
-
-      microblocks =
-        Enum.map(1..10, fn i ->
-          # credo:disable-for-next-line
-          mb_tag = String.to_atom("mb#{i}")
-          user = String.to_existing_atom("user#{i}")
-          oracle_id = :aeser_id.create(:oracle, <<i::256>>)
-
-          {
-            mb_tag,
-            [
-              tx1:
-                name_tx(:name_update_tx, user, "name#{i}.chain", %{
-                  pointers: [{:pointer, "account_pubkey", user}]
-                }),
-              tx2: {:oracle_query_tx, user, oracle_id, %{}}
-            ] ++
-              Enum.map(3..50, fn i ->
-                tx_tag = String.to_existing_atom("tx#{i}")
-                user = String.to_existing_atom("user#{i}")
-                {tx_tag, spend_tx(user, user, 1_000)}
-              end)
-          }
-        end)
-
-      with_blockchain accounts, [first_microblock | microblocks] do
-        %{hash: last_mb_hash, height: 10} = blocks[:mb10]
-        last_mb_hash = AeMdw.Validate.id!(last_mb_hash)
-
-        assert mem1 = :ets.info(:sync_hashes, :memory)
-        assert {height_blocks, txi} = Block.blocks_mutations(0, 0, 0, last_mb_hash)
-        assert {^height_blocks, ^txi} = Block.blocks_mutations(0, 0, 0, last_mb_hash)
-        assert length(height_blocks) == 11
-        assert mem2 = :ets.info(:sync_hashes, :memory)
-        assert mem2 > mem1
-      end
-    end
-  end
-end