I feel like I’m at an impasse in my career - what is the minimum intelligence required to be successful as a software engineer? Or is it more useful for a lower intelligence individual like me to pick a different career path?
While test scores might be indicative of your aptitudes at different types of problems, unless you're actually struggling with your work, it mightn't be a problem.
There's plenty of successful software engineers who've interviewed/tested unsuccessfully at Google/Facebook/Microsoft/etc, and gone on to have rewarding and fulfilling careers. Some people are just bad at interviews. And some interviews are just looking for a particular type of person, and not everyone who's a good engineer is going to fit that profile.
Do you enjoy your work? Is it stimulating and challenging and sometimes even fun?
Do you feel like you understand the tradeoffs in making the choices you make while coding? And if not, it that because you find them just baffling? Or because you understand it, but don't have the experience or knowledge to really make a clear decision yet?
The VAST majority of coding has basically nothing to do with maths. You need to be able to think logically, break things down from high level goals to low level steps, and be tenacious in working through design issues and coding bugs.
And, having said of all that, not everyone has to be a genius coder either. The other 99% of software engineers do a decent job, nothing too stellar (but hopefully nothing too crap either). It's ok to not be the best in the world.
My advice would be to stop worrying about scores (IQ, SAT, whatever) — you’re not in high school any more. And stop comparing yourself to other people.
Are you meeting expectations at work? Getting solid reviews from your manager? That’s what matters.
So you don’t test well? So you didn’t get into the big name companies that have famously grueling interview processes and reject the vast, vast majority of candidates? So what?
There are plenty of other companies out there that need your skills. Badly.
Yes, a bunch of them cargo cult the same ridiculous interview processes as the FAANGs. But not all of them do.
Find the ones that don’t. Find the ones that instead send you a small take-home that mirrors the type of work you’ll be doing daily. Show them that even if you may not be good at solving algorithmic puzzles under pressure, you’re good at writing software.
That’s what matters.
For coding interviews, to do well, work through all of the hackerrank.com or the equivalent problem sets in your preferred language. At some point you will see the "algorithmic" or "data structure" patterns in the problem sets and you will be able to go forth. I am not sure these even predict job performance though but they are the price you have to pay to "get in".
Also I think the average engineer at a FAANGM company takes 2-3 interviews to actually get in as well. So look at it as a challenge and learning opportunity rather.
For what it's worth, I'm QA and I've got a measured IQ in the mid 80's. Thus far I've had no complaints from anyone about it.
Actual posts from people with low IQ read more like 3+ replies deep in the comments section on a controversial political video on YouTube.
You sound like you have testing anxiety, insecurities, self-confidence issues, self-esteem issues, and self-doubt. The word choice of your post and the way you explain what is going on suggests you have sufficient intelligence. It seems like the biggest blocks to being successful in this field you have are believing in yourself and judging yourself. You keep thinking you should be further along and working at a "better" company. You keep comparing yourself to others and their path.
Stop.
Your life is your own, your path is your own. Your background is your own. Your challenges and dreams are your own. Don't expect your experience to be like everyone else's. There are a wide variety of successful developers from hugely different backgrounds. Some people could only go to a local collage or state university. Some people don't even have a CS degree and are still successful. I know some people with only high school-level education that can debug applications with with a time-travel trace looking at the assembly language level. Many of the people who created the popular frameworks and programming languages don't have the background you would expect. And honestly there are even a few positions at some really well known companies where even below average intelligence people can be successful. There are successful developers who have never worked at a FAANG company and probably never will.
Work on confidence, self-esteem, self-worth, and believing in yourself. Stop judging yourself.
Don't let getting into a FAANG company be your measuring stick of what success is, make that a goal instead. Plenty of people found that when they actually got to a FAANG company, they didn't actually like it, or didn't end up staying very long.
I would ask yourself these questions to see if you are successful:
Are you enjoying your current job?
Are you learning at your current job? / Does your current job prepare you for future jobs?
Are you being paid well at your current job?
Do the benefits of your current job meet your needs?
If you can consistently answer yes to these questions, then you are successful. These are also a good barometer of when to ask for a raise or look for a new job.