You've completely missed the point. If you need to do this every time you change jobs, then throughout your career you're spending years! of your life on interview prep. Getting into Google for the first time, sure, it's worth it then. But what about the next job? Or the job after that?
I've always just kind of assumed that everyone does a fair amount of interview prep. Maybe not a month, but at least a week or so to refresh your interviewing skills and practice. The skills needed to pass an interview have almost nothing to do with the skills you're employing day-to-day in your job, so you should expect them to get weaker the longer it's been since you've applied for a job.
I mean, what do you guys do, just walk in and wing it?
Ok, so I generally do research about the business to make sure I understand the problems they are solving and have good questions to ask, but never CS interview prep. And I'm not some coding genius...I couldn't rattle off big-o for any algorithm off the top of my head, for instance...maybe a little above average.
Then again, I've only worked for 5 employers in a 19 year career. I think that was something like 18 interviews total in my career. A grand total of 1 or 2 required any deep CS knowledge and those were questions like "write fibonnaccci on the whiteboard*" or write a linked list in a code editor. I don't consider those to be worth studying...you should be able to do those off the cuff. And also, I'm pretty sure I can come up with a reasonable solution to most problems presented under pressure...something I know throws some people off.
Anyway, those 18 interviews yielded something like 9 or 10 job offers. And the fibonacci one...no offer...stared at it for 5 minutes after getting stuck on one of the conditionals before finding my mistake and didn't get the job. But whatever. There are always more interviews.
Now, I've also never approached a job like "I really want to work at Google/Apple/Facebook/etc so I have to ace this interview". I've always taken a broader, more laissez faire approach to try to find the right fit for me. So it might just be a matter of your approach to a job hunt.
I used to prepare for about a week every time I switched jobs early in my career. That's back when every company just asked typical DS&A whiteboard questions. Now, every company has its own method. I don't bother to prepare because I never know what I'm walking into. I just wing it.
This comment[0] says it better than I can:
unless you're interviewing at one of the big companies with a known interview process, you'd basically be wasting your time.
I've done hundreds of tech interviews over my career, and especially in recent years (now that companies are trying new things), it's completely random.
Some will do "Cracking the coding interview" type shit, some will do code reviews, some will give you a take home thing you have to present, some will do pair coding. Some do algorithms only, some do design discussions only, and so on and so forth.
So any prep I do will be a shot in the dark and 99% of the time I'll have to do something I did not prep for. So I don't bother trying.
Notable exception is my current job, which is a big tech co with a semi well known interview process (not as infamous as google or facebook, but still), and they gave me a fair amount of info up front. I also -really really really- wanted to work there because the team I wanted to work for did things no one else does. So i bit the bullet and studied/practice.
That was literally the first time (and probably last) time I did.
I dunno, I just ask for raises based on what I did in the past year. I've heard many employers say no, but if they don't want to lose you and you have a good case (management loves numbers, show them numbers) you should get it...
