Best thing you can do is to enhance your skills in data structures and algorithms so you have a strong base in them. The interviews normally start here for most of these companies because their software deals with a large amount of data structures and/or algorithms and is essential to understand to be a productive contributor there.

If your previous work did not actually require you to know them, they probably where not building algorithms from scratch or optimizing parsing/processing of data very much. As without the essential basics of data structures and algorithms it is very hard to build scalable applications that rely on them.

As you grow in your career you will have to learn things outside of your base knowledge as you move up the ranks on the technical skills ladder. This will be standard requirements for senior level positions which you are probably seeing now. At the junior and mid level you are normally not responsible for building the core pieces of data processing software engines or massively scalable applications that run custom in house algorithms.

If you go through some of the below resources they should help fill that skills gap and make you an overall stronger engineer so you can feel confident applying for senior level positions.

I would recommend taking the following course: https://www.coursera.org/specializations/data-structures-alg... https://www.edx.org/course/algorithms-and-data-structures https://in.udacity.com/course/data-structures-and-algorithms...

and reading the following book: https://www.amazon.com/Introduction-Algorithms-Press-Thomas-...