What topic of article to choose?

I writing article in my university second time, first time I wrote about passwords hashing. I liked that title cause: 1)its refers to web development and mobile too, so its very useful; 2)I could wrote and experimented with hash functions and showed my code and results in article. Now I need to write second adrticle and I dont know what title choose yet, but I want something useful for junior developer with code review like my previous article. Do you have any ideas?