Basically, we use buildUserService method to create and configure UserService instance. Also it is not going to impact the app memory on large scale unless it is called frequently in a loop.
But we do have an alternate way to avoid this case, instead of using buildUserService method, you can create UserService instance as follows:
UserService *userService = [[UserService alloc] initWithAPIKey:@"APP_Key" secretKey:@"SECRET_Key"];
Please let us know if the problem continues.