diff --git a/avers-server.cabal b/avers-server.cabal
--- a/avers-server.cabal
+++ b/avers-server.cabal
@@ -1,5 +1,5 @@
 name:                avers-server
-version:             0.0.1
+version:             0.0.2
 synopsis:            Server implementation of the Avers API
 description:         See README.md
 homepage:            http://github.com/wereHamster/avers-server
@@ -33,9 +33,11 @@
    , aeson
    , avers
    , avers-api
+   , base64-bytestring
    , bytestring
    , bytestring-conversion
    , cookie
+   , cryptohash
    , either
    , http-types
    , mtl
diff --git a/src/Avers/Server.hs b/src/Avers/Server.hs
--- a/src/Avers/Server.hs
+++ b/src/Avers/Server.hs
@@ -25,7 +25,8 @@
 -- import qualified Data.Text            as T
 import qualified Data.Text.Encoding   as T
 
-import qualified Data.ByteString.Lazy as LBS
+import qualified Data.ByteString.Lazy   as LBS
+import qualified Data.ByteString.Base64 as BS64
 
 
 import Data.Monoid
@@ -33,9 +34,11 @@
 -- import Data.Proxy
 -- import Data.Maybe
 import Data.Time
-import Data.Aeson (encode, decode)
+import Data.Aeson (ToJSON, encode, decode)
 -- import Data.Aeson.TH (defaultOptions)
 
+import Crypto.Hash.SHA256 (hashlazy)
+
 import Servant.API
 import Servant.Server
 
@@ -60,8 +63,14 @@
 
 import Web.Cookie
 
+import Prelude
 
 
+
+etagVersion :: Text
+etagVersion = "v0"
+
+
 -- | Convert the 'Credentials' into an 'ObjId' to which the ceredentials refer.
 -- That's the object the client is authenticated as.
 credentialsObjId :: Handle -> Credentials -> EitherT ServantErr IO ObjId
@@ -99,7 +108,15 @@
 reqAvers aversH m = liftIO (evalAvers aversH m) >>= aversResult
 
 
+cacheableResponse :: (ToJSON a) => Maybe Text -> a -> EitherT ServantErr IO (Cacheable a)
+cacheableResponse mbValidationToken a = do
+    let etag = T.decodeUtf8 $ BS64.encode $ hashlazy $ encode a
+    if mbValidationToken == Just (etagVersion <> ":" <> etag)
+        then left $ err304
+        else pure $ addHeader "no-cache, public, max-age=63072000"
+                  $ addHeader (etagVersion <> ":" <> etag) a
 
+
 serveAversCoreAPI :: Handle -> Authorizations -> Server AversCoreAPI
 serveAversCoreAPI aversH auth =
          serveCreateObject
@@ -138,7 +155,7 @@
 
     ----------------------------------------------------------------------------
     -- LookupObject
-    serveLookupObject objId cred = do
+    serveLookupObject objId cred validationToken = do
         runAuthorization aversH $
             lookupObjectAuthz auth cred objId
 
@@ -149,7 +166,7 @@
 
             pure (object, snapshot)
 
-        pure $ LookupObjectResponse
+        cacheableResponse validationToken $ LookupObjectResponse
             { lorId = objId
             , lorType = objectType
             , lorCreatedAt = objectCreatedAt
@@ -181,7 +198,7 @@
             }
 
     serveDeleteObject _ _ = left err500
-    serveLookupPatch _ _ _ = left err500
+    serveLookupPatch _ _ _ _ = left err500
 
 
     ----------------------------------------------------------------------------
@@ -224,8 +241,8 @@
 
 
     serveCreateRelease _ _ _ = left err500
-    serveLookupRelease _ _ _ = left err500
-    serveLookupLatestRelease _ _ = left err500
+    serveLookupRelease _ _ _ _ = left err500
+    serveLookupLatestRelease _ _ _ = left err500
     serveChangeSecret _ _ = left err500