I've been interviewed by some experienced engineer, when he strongly disagreed with some statements I said:
Assuming full control over your applications, It's a standard practice to make writes-to-database exclusive to one single application or controller (not about multiple application instances, but different applications).
Assuming full control over design, synchronization is better implemented using observer pattern than using polling from both ends.
I'd really like for some experienced engineers to enlighten me on those 2 main points, and point to me if I've been right/wrong about them.