diff --git a/amazonka-core.cabal b/amazonka-core.cabal
--- a/amazonka-core.cabal
+++ b/amazonka-core.cabal
@@ -1,6 +1,6 @@
 name:                  amazonka-core
-version:               0.0.0
-synopsis:              Core functionality, serialisation primitives, and data types for the amazonka Amazon Web Services SDKs.
+version:               0.0.1
+synopsis:              Core functionality, serialisation primitives, and data types for the Amazonka Amazon Web Services SDKs.
 homepage:              https://github.com/brendanhay/amazonka
 license:               OtherLicense
 license-file:          LICENSE
@@ -14,7 +14,7 @@
 
 description:
     Core functionality, serialisation primitives, and data types for
-    amazonka related Amazon Web Services SDKs.
+    Amazonka related Amazon Web Services SDKs.
     .
     /Warning:/ This is an experimental preview release which is still under
     heavy development and not intended for public consumption, caveat emptor!
diff --git a/src/Network/AWS/Auth.hs b/src/Network/AWS/Auth.hs
--- a/src/Network/AWS/Auth.hs
+++ b/src/Network/AWS/Auth.hs
@@ -108,8 +108,10 @@
     FromSession a s t -> return (fromSession a s t)
     FromProfile n     -> show `withExceptT` fromProfileName m n
     FromEnv     a s   -> fromEnvVars a s
-    Discover          ->
-        fromEnv `catchError` const (show `withExceptT` fromProfile m)
+    Discover          -> fromEnv `catchError` const (iam `catchError` (const err))
+      where
+        iam = show `withExceptT` fromProfile m
+        err = throwError "Unable to read environment variables or IAM profile."
 
 -- | Retrieve access and secret keys from the default environment variables.
 --
diff --git a/src/Network/AWS/Data/Internal/ByteString.hs b/src/Network/AWS/Data/Internal/ByteString.hs
--- a/src/Network/AWS/Data/Internal/ByteString.hs
+++ b/src/Network/AWS/Data/Internal/ByteString.hs
@@ -48,12 +48,14 @@
 
 showBS :: ToByteString a => a -> String
 showBS = BS.unpack . toBS
+{-# INLINE showBS #-}
 
 class ToByteString a where
     toBS :: a -> ByteString
 
     default toBS :: ToText a => a -> ByteString
     toBS = Text.encodeUtf8 . toText
+    {-# INLINE toBS #-}
 
 instance ToByteString Builder    where toBS = buildBS
 instance ToByteString ByteString where toBS = id
@@ -71,12 +73,14 @@
 
 buildBS :: ToBuilder a => a -> ByteString
 buildBS = LBS.toStrict . Build.toLazyByteString . build
+{-# INLINE buildBS #-}
 
 class ToBuilder a where
     build :: a -> Builder
 
     default build :: ToByteString a => a -> Builder
     build = build . toBS
+    {-# INLINE build #-}
 
 instance ToBuilder Builder    where build = id
 instance ToBuilder ByteString where build = Build.byteString
@@ -92,3 +96,4 @@
 
 stripBS :: ByteString -> ByteString
 stripBS = BS.dropWhile isSpace . fst . BS.spanEnd isSpace
+{-# INLINE stripBS #-}
diff --git a/src/Network/AWS/Data/Internal/Header.hs b/src/Network/AWS/Data/Internal/Header.hs
--- a/src/Network/AWS/Data/Internal/Header.hs
+++ b/src/Network/AWS/Data/Internal/Header.hs
@@ -53,37 +53,55 @@
   where
     note Nothing  = Left (BS.unpack $ "Unable to find header: " <> CI.original k)
     note (Just x) = Right x
+{-# INLINE (~:) #-}
 
 (~:?) :: FromText a => ResponseHeaders -> HeaderName -> Either String (Maybe a)
 hs ~:? k =
     maybe (Right Nothing)
           (fmap Just . fromText . Text.decodeUtf8)
           (k `lookup` hs)
+{-# INLINE (~:?) #-}
 
 class ToHeaders a where
     toHeaders :: a -> [Header]
     toHeaders = const mempty
+    {-# INLINE toHeaders #-}
 
 (=:) :: ToHeader a => HeaderName -> a -> [Header]
 (=:) = toHeader
+{-# INLINE toHeaderText #-}
 
+-- FIXME: Improve complexity
 hdr :: HeaderName -> ByteString -> [Header] -> [Header]
 hdr k v hs = let h = (k, v) in deleteBy ((==) `on` fst) h hs ++ [h]
+{-# INLINE hdr #-}
 
 hdrs :: [Header] -> [Header] -> [Header]
 hdrs xs ys = Fold.foldr' (uncurry hdr) ys xs
+{-# INLINE hdrs #-}
 
+toHeaderText :: ToText a => HeaderName -> a -> [Header]
+toHeaderText k = toHeader k . toText
+
 class ToHeader a where
     toHeader :: HeaderName -> a -> [Header]
 
+    default toHeader :: ToText a => HeaderName -> a -> [Header]
+    toHeader k = toHeader k . toText
+    {-# INLINE toHeader #-}
+
 instance ToHeader Text where
     toHeader k = toHeader k . Text.encodeUtf8
+    {-# INLINE toHeader #-}
 
 instance ToHeader ByteString where
     toHeader k = toHeader k . Just
+    {-# INLINE toHeader #-}
 
 instance ToByteString a => ToHeader (Maybe a) where
     toHeader k = maybe [] (\v -> [(k, toBS v)])
+    {-# INLINE toHeader #-}
 
 instance (ToByteString k, ToByteString v) => ToHeader (HashMap k v) where
     toHeader p = map (\(k, v) -> (p <> CI.mk (toBS k), toBS v)) . Map.toList
+    {-# INLINE toHeader #-}
diff --git a/src/Network/AWS/Data/Internal/Query.hs b/src/Network/AWS/Data/Internal/Query.hs
--- a/src/Network/AWS/Data/Internal/Query.hs
+++ b/src/Network/AWS/Data/Internal/Query.hs
@@ -109,25 +109,33 @@
 
 class ToQuery a where
     toQuery :: a -> Query
-    toQuery = const mempty
 
+    default toQuery :: ToText a => a -> Query
+    toQuery = toQuery . toText
+    {-# INLINE toQuery #-}
+
 instance ToQuery Query where
     toQuery = id
+    {-# INLINE toQuery #-}
 
 instance (ToByteString k, ToQuery v) => ToQuery (k, v) where
     toQuery (k, v) = Pair (toBS k) (toQuery v)
+    {-# INLINE toQuery #-}
 
 instance (ToByteString k, ToByteString v) => ToQuery (k, Maybe v) where
     toQuery (k, v) = Pair (toBS k) . Value $ toBS <$> v
+    {-# INLINE toQuery #-}
 
 instance ToQuery Char where
     toQuery = toQuery . BS.singleton
+    {-# INLINE toQuery #-}
 
 instance ToQuery ByteString where
     toQuery "" = Value Nothing
     toQuery bs = Value (Just bs)
+    {-# INLINE toQuery #-}
 
-instance ToQuery Text    where toQuery = toQuery . toBS
+instance ToQuery Text    where toQuery = toQuery . Text.encodeUtf8
 instance ToQuery Int     where toQuery = toQuery . toBS
 instance ToQuery Integer where toQuery = toQuery . toBS
 instance ToQuery Double  where toQuery = toQuery . toBS
@@ -137,11 +145,14 @@
     toQuery = List . zipWith (\n v -> Pair (toBS n) (toQuery v)) idx
       where
         idx = [1..] :: [Integer]
+    {-# INLINE toQuery #-}
 
 instance ToQuery a => ToQuery (Maybe a) where
     toQuery (Just x) = toQuery x
     toQuery Nothing  = mempty
+    {-# INLINE toQuery #-}
 
 instance ToQuery Bool where
     toQuery True  = toQuery ("true"  :: ByteString)
     toQuery False = toQuery ("false" :: ByteString)
+    {-# INLINE toQuery #-}
diff --git a/src/Network/AWS/Data/Internal/Text.hs b/src/Network/AWS/Data/Internal/Text.hs
--- a/src/Network/AWS/Data/Internal/Text.hs
+++ b/src/Network/AWS/Data/Internal/Text.hs
@@ -46,13 +46,16 @@
 
 fromText :: FromText a => Text -> Either String a
 fromText = AText.parseOnly parser
+{-# INLINE fromText #-}
 
 -- FIXME: improve the error messages for partial match, or extra input etc.
 match :: Text -> a -> Parser a
 match x y = AText.string x <* AText.endOfInput >> return y
+{-# INLINE match #-}
 
 matchCI :: Text -> a -> Parser a
 matchCI x y = AText.asciiCI x <* AText.endOfInput >> return y
+{-# INLINE matchCI #-}
 
 class FromText a where
     parser :: Parser a
@@ -66,24 +69,30 @@
 
 instance FromText Bool where
     parser = matchCI "false" False <|> matchCI "true" True
+    {-# INLINE parser #-}
 
 showText :: ToText a => a -> String
 showText = Text.unpack . toText
+{-# INLINE showText #-}
 
 class ToText a where
     toText :: a -> Text
 
 instance (ToText a, ToText b) => ToText (a, b) where
     toText (a, b) = "(" <> toText a <> ", " <> toText b <> ")"
+    {-# INLINE toText #-}
 
 instance ToText a => ToText [a] where
     toText xs = "[" <> Text.intercalate ", " (map toText xs) <> "]"
+    {-# INLINE toText #-}
 
 instance ToText a => ToText (CI a) where
     toText = toText . CI.original
+    {-# INLINE toText #-}
 
 instance ToText (Response a) where
     toText rs = Text.pack . show $ rs { responseBody = () }
+    {-# INLINE toText #-}
 
 instance ToText Text       where toText = id
 instance ToText ByteString where toText = Text.decodeUtf8
@@ -98,6 +107,8 @@
 instance ToText Bool where
     toText True  = "true"
     toText False = "false"
+    {-# INLINE toText #-}
 
 shortText :: Builder -> Text
 shortText = LText.toStrict . Build.toLazyTextWith 32
+{-# INLINE shortText #-}
diff --git a/src/Network/AWS/Data/Internal/XML.hs b/src/Network/AWS/Data/Internal/XML.hs
--- a/src/Network/AWS/Data/Internal/XML.hs
+++ b/src/Network/AWS/Data/Internal/XML.hs
@@ -138,9 +138,15 @@
 {-# INLINE withElement #-}
 
 findElement :: Text -> [Node] -> Either String [Node]
-findElement n = maybe err Right . listToMaybe . mapMaybe (childNodes n)
+findElement n ns = maybe err Right . listToMaybe $ mapMaybe (childNodes n) ns
   where
-    err = Left $ "unable to find element " ++ show n
+    err = Left $ "unable to find element "
+        ++ show n
+        ++ " in nodes "
+        ++ show (mapMaybe name ns)
+
+    name (NodeElement e) = Just (nameLocalName (elementName e))
+    name _               = Nothing
 {-# INLINE findElement #-}
 
 childNodes :: Text -> Node -> Maybe [Node]
diff --git a/src/Network/AWS/Error.hs b/src/Network/AWS/Error.hs
--- a/src/Network/AWS/Error.hs
+++ b/src/Network/AWS/Error.hs
@@ -2,6 +2,7 @@
 {-# LANGUAGE FlexibleContexts  #-}
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE RecordWildCards   #-}
+{-# LANGUAGE TemplateHaskell   #-}
 {-# LANGUAGE TypeFamilies      #-}
 {-# LANGUAGE ViewPatterns      #-}
 
@@ -18,10 +19,12 @@
 module Network.AWS.Error where
 
 import           Control.Applicative
+import           Control.Lens
 import           Control.Monad
 import           Data.Aeson
-import qualified Data.ByteString.Lazy as LBS
-import           Data.Text            (Text)
+import qualified Data.ByteString.Lazy       as LBS
+import           Data.ByteString.Lazy.Char8 (unpack)
+import           Data.Text                  (Text)
 import           GHC.Generics
 import           Network.AWS.Data
 import           Network.AWS.Types
@@ -48,6 +51,8 @@
     , _msgRESTMessage :: Text
     } deriving (Eq, Ord, Show, Generic)
 
+makeLenses ''RESTMessage
+
 instance FromXML RESTMessage where
     parseXML x = RESTMessage
         <$> x .@ "Type"
@@ -59,6 +64,8 @@
     , _errRequestId :: Text
     } deriving (Eq, Show, Generic)
 
+makeLenses ''RESTError
+
 instance FromXML RESTError where
     parseXML x = RESTError
         <$> x .@ "Error"
@@ -71,33 +78,24 @@
           -> Maybe (LBS.ByteString -> ServiceError (Er a))
 restError f Service{..} s
     | f s       = Nothing
-    | otherwise = Just (either failure success . (decodeXML >=> parseXML))
+    | otherwise = Just go
   where
-    success = ServiceError _svcAbbrev s
-    failure = SerializerError _svcAbbrev
-
--- cloudfront
--- autoscaling
-
--- <ErrorResponse xmlns="http://cloudfront.amazonaws.com/doc/2014-10-21/">
---    <Error>
---       <Type>Sender</Type>
---       <Code>InvalidURI</Code>
---       <Message>Could not parse the specified URI.</Message>
---    </Error>
---    <RequestId>410c2a4b-e435-49c9-8382-3770d80d7d4c</RequestId>
--- </ErrorResponse>
+    go x = either failure success (decodeXML x >>= parseXML)
+      where
+        failure e = SerializerError _svcAbbrev (e ++ ":\n" ++ unpack x)
+        success   = ServiceError _svcAbbrev s
 
 data JSONError = JSONError
-    { _errType    :: Text
+    { _errType    :: Maybe Text
     , _errMessage :: Text
     } deriving (Eq, Show, Generic)
 
+makeLenses ''JSONError
+
 instance FromJSON JSONError where
-    parseJSON = withObject "JSONError" $ \o ->
-        JSONError
-            <$> o .: "__type"
-            <*> o .: "message"
+    parseJSON = withObject "JSONError" $ \o -> JSONError
+        <$> (o .:? "__type"  <|> o .:? "Type")
+        <*> (o .:  "message" <|> o .:  "Message")
 
 jsonError :: FromJSON (Er a)
           => (Status -> Bool)
@@ -106,9 +104,9 @@
           -> Maybe (LBS.ByteString -> ServiceError (Er a))
 jsonError f Service{..} s
     | f s       = Nothing
-    | otherwise = Just (either failure success . eitherDecode')
+    | otherwise = Just go
   where
-    success = ServiceError _svcAbbrev s
-    failure = SerializerError _svcAbbrev
-
--- {"__type":"ResourceNotFoundException","message":"Unable to find instance with ID 1"}
+    go x = either failure success (eitherDecode' x)
+      where
+        failure e = SerializerError _svcAbbrev (e ++ ":\n" ++ unpack x)
+        success   = ServiceError _svcAbbrev s
diff --git a/src/Network/AWS/Signing/Internal.hs b/src/Network/AWS/Signing/Internal.hs
--- a/src/Network/AWS/Signing/Internal.hs
+++ b/src/Network/AWS/Signing/Internal.hs
@@ -37,7 +37,7 @@
         -> Region    -- ^ AWS Region.
         -> Request a -- ^ Request to presign.
         -> UTCTime   -- ^ Signing time.
-        -> Int       -- ^ Expiry time in seconds.
+        -> UTCTime   -- ^ Expiry time.
         -> m (Signed a (Sg (Sv a)))
 presign a r rq t x = withAuth a $ \e -> return $
     presigned e r rq defaultTimeLocale t x
diff --git a/src/Network/AWS/Signing/V4.hs b/src/Network/AWS/Signing/V4.hs
--- a/src/Network/AWS/Signing/V4.hs
+++ b/src/Network/AWS/Signing/V4.hs
@@ -81,8 +81,7 @@
               pair "X-AMZ-Algorithm"      algorithm
             . pair "X-AMZ-Credential"     cs
             . pair "X-AMZ-Date"           (LocaleTime l t :: ISO8601)
-            . pair "X-AMZ-Expires"        x
-            . pair "X-AMZ-SignedHeaders"  sh
+            . pair "X-AMZ-Expires"        (LocaleTime l x :: ISO8601)
             . pair "X-AMZ-SignedHeaders"  sh
             . pair "X-AMZ-Security-Token" (toBS <$> _authToken a)
 
@@ -153,7 +152,7 @@
 
     headers = sortBy (comparing fst)
         . hdr hHost host'
-        . hdr hDate (toBS (LocaleTime l t :: RFC822))
+        . hdr hDate (toBS (LocaleTime l t :: ISO8601))
         $ _rqHeaders
 
     joinedHeaders = map f $ groupBy ((==) `on` fst) headers
diff --git a/src/Network/AWS/Types.hs b/src/Network/AWS/Types.hs
--- a/src/Network/AWS/Types.hs
+++ b/src/Network/AWS/Types.hs
@@ -240,7 +240,7 @@
               -> Request a
               -> TimeLocale
               -> UTCTime
-              -> Int
+              -> UTCTime
               -> Signed a v
 
 -- | Access key credential.