Amazon is down 30%, and the sorts of tech companies that will be populating this list are already down anywhere from 50% to 90%. However, the biggest pain to come is private market startups. An easy call to make, simply because you can't directly profit from it, which lets the inefficiency persist. For now.
We only need to go back a couple of years to mid 2020 when every company was laying people off. Layoffs.fyi was tracking multiple new rounds every day. I fear what is coming is going to be that or worse.
- hoard cash, i.e. don't spend it on things you don't need right now, you might need it a lot more in 6-12 months just to pay the mortgage
-do anything and everything you can to have a nest egg that will give you 18-24 months of living expenses; 6 months won't be enough for a lot of people. Not easy for everyone I know, but if the SRHTF, it might take you that long to find a new job - and that new job might not pay as well as your old one.
-get out of debt if you can. Again, not easy, but owning a house and car free-and-clear is an awesome feeling when the economy goes into a bad recession and you don't risk losing your house as long as you can pay taxes and insurance.
-get a side-gig or two on top of your job if you can, having a few irons in the fire is never a bad idea if you can handle the extra work.
-not a good time to switch jobs to a risky small tech company (or even a big tech company) if they never, or rarely make money - sooner or later VC's will stop writing checks to companies that don't have a prospect of becoming profitable - in a severe downturn, VC's will cut their losses and move on; these types of companies will be hit the hardest.
-if you are working at mega-corp, try to get on - or stay on a team that supports or develops projects that are really important to the core company functions and/or makes them money. Not a good time to be part of a 'special group' exploring some new technology pr product that might not ever pan out - when big corps tighten belts, look for those types of projects to get shut down.
Have enough cash to keep you afloat for at least 6+ months of unemployment.
If that's not currently the situation try to cut back expenses where you can to reach that state (to a reason), and imo even on the expense of 401k contributions (but please remember to start again once you have enough cash).