Hi all, I've got some "newbie" problems using MongoDB as backend in Persistent. Basically I've got my app type defined as: data MyApp = MyApp { getStatic :: Static -- ^ Settings for static file serving. , connPool :: ConnPool Host } And I made it an instance of YesodPersist by: instance YesodPersist MyApp where type YesodDB MyApp = MongoDBReader Host runDB db = liftIOHandler $ fmap connPool getYesod >>= (\p -> return (p, "localhost")) >>= runMongoDBConn db And I made it an instance of YesodAuth as well by: instance YesodAuth MyApp where type AuthId MyApp = UserId loginDest _ = RootR logoutDest _ = RootR getAuthId creds = runDB $ do x <- getBy $ UniqueUser $ credsIdent creds case x of Just (uid, _) -> return $ Just uid Nothing -> do fmap Just $ insert $ User (credsIdent creds) Nothing authPlugins = [ authEmail ] I've defined User model as yesod scaffold tool defines it. Now, when I try to compile it i get: No instances for (Control.Monad.Context.Context Database.MongoDB.Connection.MasterOrSlaveOk (GGHandler s MyApp IO), Control.Monad.Context.Context Database.MongoDB.Query.Database (GGHandler s MyApp IO), Control.Monad.Context.Context Database.MongoDB.Internal.Protocol.Pipe (GGHandler s MyApp IO), Control.Monad.Context.Context Database.MongoDB.Query.WriteMode (GGHandler s MyApp IO), Control.Monad.Throw.Throw Database.MongoDB.Query.Failure (GGHandler s MyApp IO)) arising from a use of `insert' Possible fix: add instance declarations for (Control.Monad.Context.Context Database.MongoDB.Connection.MasterOrSlaveOk (GGHandler s MyApp IO), Control.Monad.Context.Context Database.MongoDB.Query.Database (GGHandler s MyApp IO), Control.Monad.Context.Context Database.MongoDB.Internal.Protocol.Pipe (GGHandler s MyApp IO), Control.Monad.Context.Context Database.MongoDB.Query.WriteMode (GGHandler s MyApp IO), Control.Monad.Throw.Throw Database.MongoDB.Query.Failure (GGHandler s MyApp IO)) In the expression: insert In the second argument of `($)', namely `insert $ User (credsIdent creds) Nothing' In the expression: fmap Just $ insert $ User (credsIdent creds) Nothing The problem is probably very trivial.. But I've got no ideas how to fix it. Best regards Kamil Ciemniewski