diff --git a/services/federator/federator.cabal b/services/federator/federator.cabal
index 0b26b11d71a..308f6966089 100644
--- a/services/federator/federator.cabal
+++ b/services/federator/federator.cabal
@@ -1,10 +1,10 @@
 cabal-version: 1.12
 
--- This file has been generated from package.yaml by hpack version 0.31.2.
+-- This file has been generated from package.yaml by hpack version 0.33.0.
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: 05e45399becaef2bbecfa958ec4d5633900e2e1d8e1c1a2e7ecd2afbdbc2404f
+-- hash: 72597caf8878551b0609bfdc790852575f38db429ea5c83935a399c676ee3c2c
 
 name:           federator
 version:        1.0.0
@@ -20,10 +20,10 @@ library
   exposed-modules:
       Federator.API
       Federator.App
+      Federator.Impl
       Federator.Options
       Federator.Run
       Federator.Types
-      Federator.Util
   other-modules:
       Paths_federator
   hs-source-dirs:
@@ -35,14 +35,12 @@ library
     , aeson
     , base
     , bilge
-    , brig-types
     , bytestring-conversion
     , data-default
     , email-validate
     , errors
     , exceptions
     , extended
-    , galley-types
     , imports
     , lens
     , metrics-core
@@ -60,6 +58,8 @@ library
     , wai
     , wai-utilities
     , warp
+    , wire-api
+    , wire-api-federation
   default-language: Haskell2010
 
 executable federator
@@ -75,7 +75,6 @@ executable federator
     , aeson
     , base
     , bilge
-    , brig-types
     , bytestring-conversion
     , data-default
     , email-validate
@@ -83,7 +82,6 @@ executable federator
     , exceptions
     , extended
     , federator
-    , galley-types
     , imports
     , lens
     , metrics-core
@@ -101,4 +99,6 @@ executable federator
     , wai
     , wai-utilities
     , warp
+    , wire-api
+    , wire-api-federation
   default-language: Haskell2010
diff --git a/services/federator/package.yaml b/services/federator/package.yaml
index 892fe7194c8..6035999778c 100644
--- a/services/federator/package.yaml
+++ b/services/federator/package.yaml
@@ -12,14 +12,12 @@ dependencies:
 - aeson
 - base
 - bilge
-- brig-types
 - bytestring-conversion
 - data-default
 - email-validate
 - errors
 - exceptions
 - extended
-- galley-types
 - imports
 - lens
 - metrics-core
@@ -38,6 +36,8 @@ dependencies:
 - wai
 - wai-utilities
 - warp
+- wire-api
+- wire-api-federation
 library:
   source-dirs: src
 executables:
diff --git a/services/federator/src/Federator/API.hs b/services/federator/src/Federator/API.hs
index 1ea46ddd105..ba5026aee23 100644
--- a/services/federator/src/Federator/API.hs
+++ b/services/federator/src/Federator/API.hs
@@ -17,53 +17,42 @@
 -- You should have received a copy of the GNU Affero General Public License along
 -- with this program. If not, see <https://www.gnu.org/licenses/>.
 
-module Federator.API where
-
-import Brig.Types.Client.Prekey
-import Brig.Types.Test.Arbitrary ()
-import Data.Aeson.TH (deriveJSON)
-import Data.Handle (Handle (..))
-import Data.Id (UserId)
-import Data.Qualified
-import Federator.Util
+module Federator.API
+  ( Api (..),
+    module Fed,
+  )
+where
+
+import Data.Id (ConvId, UserId)
+import Data.Qualified (Qualified)
 import Imports
 import Servant.API
 import Servant.API.Generic
-import Test.QuickCheck
+import Wire.API.Federation.API.Conversation as Fed hiding (Api)
+import Wire.API.Federation.Event as Fed
+import Wire.API.User.Client.Prekey (PrekeyBundle)
 
-data API route = API
-  { _gapiSearch ::
-      route
-        :- "i"
-        :> "search"
-        -- QUESTION: what exactly should the query be? text + domain?
-        :> QueryParam' [Required, Strict] "q" (Qualified Handle)
-        :> Get '[JSON] FUser,
-    _gapiPrekeys ::
+data Api route = Api
+  { _gapiPrekeys ::
       route
         :- "i"
         :> "users"
-        :> Capture "fqu" (Qualified UserId)
+        :> Capture "id" (Qualified UserId)
         :> "prekeys"
-        :> Get '[JSON] PrekeyBundle
+        -- FUTUREWORK(federation):
+        -- this should return a version of PrekeyBundle with qualified UserId,
+        -- defined in wire-api-federation
+        :> Get '[JSON] PrekeyBundle,
+    _gapiJoinConversationById ::
+      route
+        :- "i"
+        :> "conversations"
+        :> Capture "cnv" (Qualified ConvId)
+        :> "join"
+        :> ReqBody '[JSON] Fed.JoinConversationByIdRequest
+        :> Post '[JSON] (Fed.ConversationUpdateResult Fed.MemberJoin)
   }
   deriving (Generic)
 
--- curl http://localhost:8097/i/search?q=wef@a.com; curl http://localhost:8097/i/users/`uuid`@example.com/prekeys
-
 ----------------------------------------------------------------------
--- TODO: add roundtrip tests for *HttpApiData, *JSON, ...
---
--- TODO: the client ids in the 'PrekeyBundle' aren't really needed here.  do we want to make a
--- new type for that, then?
-
-data FUser = FUser
-  { _fuGlobalHandle :: !(Qualified Handle),
-    _fuFQU :: !(Qualified UserId)
-  }
-  deriving (Eq, Show, Generic)
-
-deriveJSON (wireJsonOptions "_fu") ''FUser
-
-instance Arbitrary FUser where
-  arbitrary = FUser <$> arbitrary <*> arbitrary
+-- FUTUREWORK: add roundtrip tests for *HttpApiData, *JSON, ...
diff --git a/services/federator/src/Federator/App.hs b/services/federator/src/Federator/App.hs
index 2c375802d91..f6dcd763ab2 100644
--- a/services/federator/src/Federator/App.hs
+++ b/services/federator/src/Federator/App.hs
@@ -1,5 +1,5 @@
+{-# LANGUAGE DerivingStrategies #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
-{-# LANGUAGE RecordWildCards #-}
 
 -- This file is part of the Wire Server implementation.
 --
@@ -19,19 +19,66 @@
 -- with this program. If not, see <https://www.gnu.org/licenses/>.
 
 module Federator.App
-  ( app,
+  ( AppT,
+    AppIO,
+    runAppT,
+    runAppResourceT,
   )
 where
 
-import Data.Proxy
-import qualified Federator.API as API
-import Federator.Types
-import Network.Wai
-import Servant.API.Generic
-import Servant.Mock
-import Servant.Server
-
-app :: Env -> Application
-app _ = serve api (mock api Proxy)
-  where
-    api = Proxy @(ToServantApi API.API)
+import Bilge (RequestId (unRequestId))
+import Bilge.RPC (HasRequestId (..))
+import Control.Error (ExceptT)
+import Control.Lens (view)
+import Control.Monad.Catch (MonadCatch, MonadMask, MonadThrow)
+import Control.Monad.Trans.Resource (MonadUnliftIO, ResourceT, runResourceT, transResourceT)
+import Federator.Types (Env, applog, requestId)
+import Imports
+import Servant.API.Generic ()
+import Servant.Server ()
+import System.Logger.Class as LC
+import qualified System.Logger.Extended as Log
+
+-- FUTUREWORK: this code re-occurs in every service.  introduce 'MkAppT' in types-common that
+-- takes 'Env' as one more argument.
+newtype AppT m a = AppT
+  { unAppT :: ReaderT Env m a
+  }
+  deriving newtype
+    ( Functor,
+      Applicative,
+      Monad,
+      MonadIO,
+      MonadThrow,
+      MonadCatch,
+      MonadMask,
+      MonadReader Env
+    )
+
+type AppIO = AppT IO
+
+instance MonadIO m => LC.MonadLogger (AppT m) where
+  log l m = do
+    g <- view applog
+    r <- view requestId
+    Log.log g l $ field "request" (unRequestId r) ~~ m
+
+instance MonadIO m => LC.MonadLogger (ExceptT err (AppT m)) where
+  log l m = lift (LC.log l m)
+
+instance Monad m => HasRequestId (AppT m) where
+  getRequestId = view requestId
+
+instance MonadUnliftIO m => MonadUnliftIO (AppT m) where
+  withRunInIO inner =
+    AppT . ReaderT $ \r ->
+      withRunInIO $ \runner ->
+        inner (runner . flip runReaderT r . unAppT)
+
+runAppT :: Env -> AppT m a -> m a
+runAppT e (AppT ma) = runReaderT ma e
+
+runAppResourceT :: ResourceT AppIO a -> AppIO a
+runAppResourceT ma = do
+  e <- ask
+  liftIO . runResourceT $ transResourceT (runAppT e) ma
diff --git a/services/federator/src/Federator/Util.hs b/services/federator/src/Federator/Impl.hs
similarity index 57%
rename from services/federator/src/Federator/Util.hs
rename to services/federator/src/Federator/Impl.hs
index c947f0e0e46..75a01c5c800 100644
--- a/services/federator/src/Federator/Util.hs
+++ b/services/federator/src/Federator/Impl.hs
@@ -1,3 +1,6 @@
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE RecordWildCards #-}
+
 -- This file is part of the Wire Server implementation.
 --
 -- Copyright (C) 2020 Wire Swiss GmbH <opensource@wire.com>
@@ -15,25 +18,20 @@
 -- You should have received a copy of the GNU Affero General Public License along
 -- with this program. If not, see <https://www.gnu.org/licenses/>.
 
-module Federator.Util
-  ( wireJsonOptions,
+module Federator.Impl
+  ( app,
   )
 where
 
-import Data.Aeson as Aeson
-import Imports
-
-dropPrefix :: String -> String -> Maybe String
-dropPrefix pfx str =
-  if length pfx > length str
-    then Nothing
-    else case splitAt (length pfx) str of
-      (pfx', sfx) ->
-        if pfx' /= pfx
-          then Nothing
-          else Just sfx
+import Data.Proxy
+import qualified Federator.API as API
+import Federator.Types
+import Network.Wai
+import Servant.API.Generic
+import Servant.Mock
+import Servant.Server
 
--- | This is a partial function; totality of all calls must be verified by roundtrip tests on
--- the aeson instances involved.
-wireJsonOptions :: String -> Options
-wireJsonOptions pfx = defaultOptions {fieldLabelModifier = fromJust . dropPrefix pfx . fmap toLower}
+app :: Env -> Application
+app _ = serve api (mock api Proxy)
+  where
+    api = Proxy @(ToServantApi API.Api)
diff --git a/services/federator/src/Federator/Run.hs b/services/federator/src/Federator/Run.hs
index 1744745e1f6..023bbd0956a 100644
--- a/services/federator/src/Federator/Run.hs
+++ b/services/federator/src/Federator/Run.hs
@@ -25,32 +25,20 @@ module Federator.Run
     -- * App Environment
     newEnv,
     closeEnv,
-
-    -- * App Monad
-    AppT,
-    AppIO,
-    runAppT,
-    runAppResourceT,
   )
 where
 
-import Bilge (RequestId (unRequestId))
-import Bilge.RPC (HasRequestId (..))
-import Control.Error
-import Control.Lens (view, (^.))
-import Control.Monad.Catch (MonadCatch, MonadMask, MonadThrow)
-import Control.Monad.Trans.Resource
+import Control.Lens ((^.))
 import Data.Default (def)
 import qualified Data.Metrics.Middleware as Metrics
 import Data.Text (unpack)
-import qualified Federator.App as App
+import qualified Federator.Impl as Impl
 import Federator.Options as Opt
 import Federator.Types
 import Imports
 import Network.Wai (Application)
 import qualified Network.Wai.Handler.Warp as Warp
 import Network.Wai.Utilities.Server as Server
-import System.Logger.Class as LC
 import qualified System.Logger.Extended as Log
 import Util.Options
 
@@ -66,7 +54,7 @@ run opts = do
 mkApp :: Opts -> IO (Application, Env)
 mkApp opts = do
   env <- newEnv opts
-  pure (App.app env, env)
+  pure (Impl.app env, env)
 
 -------------------------------------------------------------------------------
 -- Environment
@@ -82,50 +70,3 @@ closeEnv :: Env -> IO ()
 closeEnv e = do
   Log.flush $ e ^. applog
   Log.close $ e ^. applog
-
--------------------------------------------------------------------------------
--- App Monad
-
--- FUTUREWORK: this code re-occurs in every service.  introduce 'MkAppT' in types-common that
--- takes 'Env' as one more argument.
-newtype AppT m a = AppT
-  { unAppT :: ReaderT Env m a
-  }
-  deriving
-    ( Functor,
-      Applicative,
-      Monad,
-      MonadIO,
-      MonadThrow,
-      MonadCatch,
-      MonadMask,
-      MonadReader Env
-    )
-
-type AppIO = AppT IO
-
-instance MonadIO m => LC.MonadLogger (AppT m) where
-  log l m = do
-    g <- view applog
-    r <- view requestId
-    Log.log g l $ field "request" (unRequestId r) ~~ m
-
-instance MonadIO m => LC.MonadLogger (ExceptT err (AppT m)) where
-  log l m = lift (LC.log l m)
-
-instance Monad m => HasRequestId (AppT m) where
-  getRequestId = view requestId
-
-instance MonadUnliftIO m => MonadUnliftIO (AppT m) where
-  withRunInIO inner =
-    AppT . ReaderT $ \r ->
-      withRunInIO $ \runner ->
-        inner (runner . flip runReaderT r . unAppT)
-
-runAppT :: Env -> AppT m a -> m a
-runAppT e (AppT ma) = runReaderT ma e
-
-runAppResourceT :: ResourceT AppIO a -> AppIO a
-runAppResourceT ma = do
-  e <- ask
-  liftIO . runResourceT $ transResourceT (runAppT e) ma