diff --git a/hbs2-storage-simple/hbs2-storage-simple.cabal b/hbs2-storage-simple/hbs2-storage-simple.cabal
index 4eccfd58..59dfc310 100644
--- a/hbs2-storage-simple/hbs2-storage-simple.cabal
+++ b/hbs2-storage-simple/hbs2-storage-simple.cabal
@@ -59,6 +59,7 @@ library
     import:           shared-properties
     exposed-modules:  HBS2.Storage.Simple
                     , HBS2.Storage.Simple.Extra
+                    , HBS2.Storage.Compact
     -- other-modules:
     -- other-extensions:
     build-depends:    base, hbs2-core
@@ -84,6 +85,7 @@ library
                     , unordered-containers
                     , temporary
                     , filepattern
+                    , unliftio
 
 
     hs-source-dirs:   lib
diff --git a/hbs2-storage-simple/lib/HBS2/Storage/Compact.hs b/hbs2-storage-simple/lib/HBS2/Storage/Compact.hs
new file mode 100644
index 00000000..48e4fb71
--- /dev/null
+++ b/hbs2-storage-simple/lib/HBS2/Storage/Compact.hs
@@ -0,0 +1,49 @@
+module HBS2.Storage.Compact
+  ( CompactStorage
+  ) where
+
+
+import Data.Word
+import Data.ByteString
+import Data.Coerce
+import Codec.Serialise
+import GHC.Generics
+import System.IO
+import UnliftIO
+
+-- compact storage
+-- for the off-tree data representation
+-- may be it will be faster, than Simple storage
+-- who knows
+
+newtype EntryOffset = EntryOffset Word64
+                      deriving newtype (Ord,Eq,Num,Enum,Real)
+                      deriving stock Generic
+
+newtype EntrySize = EntrySize Word64
+                    deriving newtype (Ord,Eq,Num,Enum,Real)
+                    deriving stock Generic
+
+data IndexEntry =
+  IndexEntry
+  { idxEntryPrev   :: Maybe Word64
+  , idxEntryOffset :: EntryOffset
+  , idxEntrySize   :: EntrySize
+  , idxEntryKey    :: ByteString
+  }
+  deriving stock Generic
+
+
+
+data CompactStorage =
+  CompactStorage
+  { csHandle :: Handle
+  }
+
+type ForCompactStorage m = MonadIO m
+
+
+compactStorageOpen :: ForCompactStorage m => FilePath -> m CompactStorage
+compactStorageOpen fp = undefined
+
+