How to prepare for a job switch?

First, I recommend going through this discussion around whether you should quit your job to focus on interview prep.

In a vacuum, I recommend doing enough to solidly meet expectations at your current job and allocating the rest of your time for interviews. The vast majority of people could really use the income from their job, so I think it's important to healthily maintain that. If you can, make this more concrete by creating an expectations plan with your manager and maintaining an honest conversation around your performance.

Another thing I recommend doing is as soon as you polish your resume, just start applying to jobs. Working a full-time job and interviewing concurrently is hard, so it's important that you spend your time well. By applying to jobs and understanding what opportunities you are getting, you can tailor your time spent accordingly. For example, you don't want to spend months grinding DSA and then not be able to land a single interview that is DSA heavy.

Thank you, Alex.
I agree with you on this statement "In a vacuum, I recommend doing enough to solidly meet expectations at your current job and allocating the rest of your time for interviews."

But, it is always said to go deep in one thing, now with Data Science work at job I feel if I am focusing on different tech stacks at the same time. How should I try to balance between different technologies?

Are you getting interviews when you apply for Software Engineering roles?

• If yes, then I'd focus on prepping the DSA parts of the interview. Spending 1-2 hours/day after work, plus weekends, should be enough to get you prepared within a few months.
• If no (you're getting ghosted or not getting to the phone screen), do not spend time on DSA prep. Instead, spend time on building projects and cultivating your network for referrals. When you have more confidence that you'll get interviews, then start doing DSA prep.

But, it is always said to go deep in one thing, now with Data Science work at job I feel if I am focusing on different tech stacks at the same time. How should I try to balance between different technologies?

In an ideal world, you can just focus on 1 thing, but it's simply very risky losing your job, especially in this economy.

Hopefully you're pretty proficient with your Data Science role and it has become more "rinse and repeat". Minimize taking on large challenges at work that require a lot of cognitive load, so you can focus as much as possible on interview preparation.