Haskell application data layer

import Data.Maybe

data User = User {
    userId :: Maybe Int,
    name :: String,
    age :: Int
} deriving (Show)

data S3Config = S3Config {
    region :: String,
    bucket :: String
} deriving (Show)

data DBConfig = DBConfig {
    host :: String,
    port :: Int
}

class UserService a where
    getUser :: a -> Int -> IO User
    updateUser :: a -> Int -> User -> IO User

instance UserService S3Config where
    getUser = getUserS3
    updateUser = updateUserS3

instance UserService DBConfig where
    getUser = getUserDB
    updateUser = updateUserDB

getUserS3 :: S3Config -> Int -> IO User
getUserS3 conf uid = do 
    putStrLn "Getting user using S3"
    return $ User (Just uid) "Some Name" 37

updateUserS3 :: S3Config -> Int -> User -> IO User
updateUserS3 conf uid user = do
    putStrLn "Updating user using S3"
    return $ User (Just uid) (name user) (age user)

getUserDB :: DBConfig -> Int -> IO User
getUserDB conf uid = do 
    putStrLn "Getting user using DB"
    return $ User (Just uid) "Some Name" 37

updateUserDB :: DBConfig -> Int -> User -> IO User
updateUserDB conf uid user = do
    putStrLn "Updating user using DB"
    return $ User (Just uid) (name user) (age user)

-- different configs for UserServic
s3Config = S3Config "us-east-1" "bucketName"
dbConfig = DBConfig "somehost" 1234

-- This is our program that may use different implementation of UserService
changeNameProgram :: UserService a => a -> Int -> String -> IO User
changeNameProgram conf uid newName = do
    found   <- getUser conf uid
    updated <- updateUser conf uid found {name = newName}
    return updated

res1 = changeNameProgram s3Config 10 "Melissa"
-- Getting user with S3
-- Updating user with S3
-- User {userId = Just 10, name = "Melissa", age = 37}

res2 = changeNameProgram dbConfig 20 "Frank"
-- Getting user with DB
-- Updating user with DB
-- User {userId = Just 20, name = "Frank", age = 37}