Prepare for Rigorous User Interactions

I am in a habit of considering my users to be malicious hackers. It's not a nice thing to say but it's essential to build a secure website/application. However, every now and then, I miss something of course.

Recently, while we were checking the logs, we saw that some data were being inserted more than once. I talked to the employees and found out that, during the workshops, no matter how many times they taught the users to only click once on buttons, they had the habit of just double or triple-clicking the buttons.

It was an easy task. I just disabled the button and showed a spinner as soon as the user clicked it. Now it didn't matter how he would interact with the form. Plus, it's a visually appealing approach.

To add to the point, I was recently traveling overseas and the airport employee wanted to print a boarding ticket for me. I wouldn't be exaggerating if I said she tapped the "next" button at least 50 times even though a busy indicator was visible on the screen asking the user to be patient while the operation is being processed.

So, whatever you do, just think of the worst kind of interaction from the user. Be prepared. There's always some user which will not read your instructions, labels and even will deliberately try to manipulate stuff.