Great idea, that's exactly what I like to do as well.

Because many people were interested in some actual code, here is an example that we used for Java:

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public class UserDao {

    private Provider<Session> sessionProvider;

    public UserDao() {
        this.sessionProvider = new DbSessionProvider();
    }

    public boolean saveUser(User user, ApiConfig config) {
        try {
            Session session = sessionProvider.get();
            session.save(user);
            System.out.println("User saved!");
            return true;
        } catch (DbException e) {
            EmailUtil.sendEmail(config.getTechnicalSupportEmail(), e);
            return false;
        }
    }

}

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"Solution": We always ask the candidate "What would you change about this code?" or something similar. We expect the candidate to come up with some selection of: - Database sessions should come an injected provider. - Configuration should probably be injected as well and not passed as a method parameter. - Booleans are not canonical Java as return value. - Don't write to stdout but to a logger. - Exception handling should probably happen outside the DAO. - Don't use static methods for sending Emails without good reason. Non-static methods are easier to test.

Finding these things is as important as being able to talk about them and give background on advantages / disadvantages of doing things different ways. With good candidates one can talk easily half an hour just about this example and adjacent topics (e.g. error handling).

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Edit: Formatting

Edit 2: added "Solution"