There's absolutely nothing wrong with talking to recruiters and going through the interview process while you're happily employed. I've done it a number of times. Often, one side or the other (ideally mutually...) decides that things aren't really lined up and you go on your ways having had some interesting conversations. I personally prefer interviewing when I'm not looking, because it's a whole lot more relaxing and low stress than trying to find a job, and if stuff moves slowly, oh well. I've had it take a year between "initial contact with a recruiter" and "starting a position" before, which isn't a big deal if you enjoy what you're doing in the meantime and have income. I generally don't move quickly in terms of employment anyway, and typically take a few months off between positions for sanity reasons and reset reasons, so the slower pace doesn't bother me at all.
I wouldn't tell your current employer you're interviewing, though - make some excuse if you're going to interview onsite, though I don't think those are things anymore...
In any case, worry about if you get an offer. There are several possibilities at that point:
- The offer, or the details of the position, aren't very interesting to you. Your current position is better, you tell them, "No, not right now," and go on with life.
- The offer is reasonable, the position is reasonable, but it's no real change over what you're doing now. At this point, you have some confirmation that your salary is sane, and you can decide if you want to stay or go. FAANGs on the resume aren't a bad option - a few years at one and you "solve" getting through HR for the rest of your career. It used to be that Microsoft on your resume would guarantee a call back, now the FAANGs (and probably still Microsoft) accomplish that, if it matters to you.
- The offer is absurdly good - they ask what you're looking for in salary, you toss out a "They'll laugh at this, but we can negotiate towards the middle..." high number, and they say, "Ok." At this point, if the position is something you're willing to do, you share the details of the offer with your current employer and see if they're willing to match it (or get closer than they are). If yes, great. You've leveraged an offer for a nice salary bump. If they don't match it, you walk and go work for the big pay bump.
All of these are common enough in my circles.
There's really no downside to the process beyond the time invested.