diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,2 +1,11 @@
+# 0.1.0.0
+
+- Using ShortByteString internally to avoid ByteString's fragmentation.
+- The default value of dbMaxSize is now 1,000.
+
+# 0.0.1.0
+
+- Supporting sessionResumeOnlyOnce.
+
 # 0.0.0.0
 - A first release.
diff --git a/Network/TLS/SessionManager.hs b/Network/TLS/SessionManager.hs
--- a/Network/TLS/SessionManager.hs
+++ b/Network/TLS/SessionManager.hs
@@ -14,12 +14,15 @@
   , newSessionManager
   ) where
 
+import Basement.Block (Block)
+import Data.ByteArray (convert)
 import Control.Exception (assert)
 import Control.Reaper
+import Data.ByteString (ByteString)
 import Data.IORef
 import Data.OrdPSQ (OrdPSQ)
 import qualified Data.OrdPSQ as Q
-import Network.TLS (SessionID, SessionData, SessionManager(..))
+import Network.TLS
 import qualified System.Clock as C
 
 import Network.TLS.Imports
@@ -36,20 +39,52 @@
     , dbMaxSize      :: !Int
     }
 
--- | Lifetime: 1 day , delay: 10 minutes, limit: 10,000 entries.
+-- | Lifetime: 1 day , delay: 10 minutes, max size: 1000 entries.
 defaultConfig :: Config
 defaultConfig = Config {
       ticketLifetime = 86400
     , pruningDelay   = 6000
-    , dbMaxSize      = 10000
+    , dbMaxSize      = 1000
     }
 
 ----------------------------------------------------------------
 
+toKey :: ByteString -> Block Word8
+toKey = convert
+
+toValue :: SessionData -> SessionDataCopy
+toValue (SessionData v cid comp msni sec mg mti malpn siz) =
+    SessionDataCopy v cid comp msni sec' mg mti malpn' siz
+  where
+    !sec' = convert sec
+    !malpn' = convert <$> malpn
+
+fromValue :: SessionDataCopy -> SessionData
+fromValue (SessionDataCopy v cid comp msni sec' mg mti malpn' siz) =
+    (SessionData v cid comp msni sec mg mti malpn siz)
+  where
+    !sec = convert sec'
+    !malpn = convert <$> malpn'
+
+----------------------------------------------------------------
+
+type SessionIDCopy = Block Word8
+data SessionDataCopy = SessionDataCopy {
+      ssVersion     :: !Version
+    , ssCipher      :: !CipherID
+    , ssCompression :: !CompressionID
+    , ssClientSNI   :: !(Maybe HostName)
+    , ssSecret      :: Block Word8
+    , ssGroup       :: !(Maybe Group)
+    , ssTicketInfo  :: !(Maybe TLS13TicketInfo)
+    , ssALPN        :: !(Maybe (Block Word8))
+    , ssMaxEarlyDataSize :: Int
+    } deriving (Show,Eq)
+
 type Sec = Int64
-type Value = (SessionData, IORef Availability)
-type DB = OrdPSQ SessionID Sec Value
-type Item = (SessionID, Sec, Value, Operation)
+type Value = (SessionDataCopy, IORef Availability)
+type DB = OrdPSQ SessionIDCopy Sec Value
+type Item = (SessionIDCopy, Sec, Value, Operation)
 
 data Operation = Add | Del
 data Use = SingleUse | MultipleUse
@@ -108,30 +143,36 @@
 establish reaper lifetime k sd = do
     ref <- newIORef Fresh
     !p <- ((+ lifetime) . C.sec) <$> C.getTime C.Monotonic
-    let !v = (sd,ref)
-    reaperAdd reaper (k,p,v,Add)
+    let !v = (sd',ref)
+    reaperAdd reaper (k',p,v,Add)
+  where
+    !k' = toKey k
+    !sd' = toValue sd
 
 resume :: Reaper DB Item -> Use
        -> SessionID -> IO (Maybe SessionData)
 resume reaper use k = do
     db <- reaperRead reaper
-    case Q.lookup k db of
+    case Q.lookup k' db of
       Nothing             -> return Nothing
       Just (p,v@(sd,ref)) -> do
            case use of
                SingleUse -> do
                    available <- atomicModifyIORef' ref check
-                   reaperAdd reaper (k,p,v,Del)
-                   return $ if available then Just sd else Nothing
-               MultipleUse -> return $ Just sd
+                   reaperAdd reaper (k',p,v,Del)
+                   return $ if available then Just (fromValue sd) else Nothing
+               MultipleUse -> return $ Just (fromValue sd)
   where
     check Fresh = (Used,True)
     check Used  = (Used,False)
+    !k' = toKey k
 
 invalidate :: Reaper DB Item
            -> SessionID -> IO ()
 invalidate reaper k = do
     db <- reaperRead reaper
-    case Q.lookup k db of
+    case Q.lookup k' db of
       Nothing    -> return ()
-      Just (p,v) -> reaperAdd reaper (k,p,v,Del)
+      Just (p,v) -> reaperAdd reaper (k',p,v,Del)
+  where
+    !k' = toKey k
diff --git a/tls-session-manager.cabal b/tls-session-manager.cabal
--- a/tls-session-manager.cabal
+++ b/tls-session-manager.cabal
@@ -1,5 +1,5 @@
 name:                tls-session-manager
-version:             0.0.1.0
+version:             0.0.2.0
 synopsis:            In-memory TLS session manager
 description:         TLS session manager with limitation, automatic pruning, energy saving and replay resistance
 license:             BSD3
@@ -18,7 +18,10 @@
   -- other-extensions:
   build-depends:       base >= 4.7 && < 5
                      , auto-update
+                     , basement
+                     , bytestring
                      , clock
+                     , memory
                      , psqueues >= 0.2.3
                      , tls
   -- hs-source-dirs: