this is something i spent a lot of time confused about during my burnout and recovery, and i've since talked to enough people to think it's a genuinely useful question that doesn't get answered cleanly.
there's a thing people say: "if you have imposter syndrome, you're probably good. only bad people don't doubt themselves." i find this... not totally true. it's comforting but it flattens something important.
imposter syndrome is REAL and common. but so is the actual skill gap. and conflating them doesn't serve you.
here's a rough framework i've been using for myself:
imposter syndrome tends to be: persistent regardless of evidence (you get positive feedback and still feel like a fraud) about your identity and worth, not specific skills activated by comparison to others, not by actual task failure something that feels different than it used to even when you haven't changed
real skill gap tends to be: specific ("i struggle with system design," not "i'm bad at everything") responsive to evidence (you fail specific tasks and that's where the feeling shows up) something you can practice and measure something your manager or peers can also see if asked
the test i've found most useful: ask a trusted senior colleague to give you a genuine read on one specific area you're worried about. not "am i good?" but "honestly, how does my SQL compared to the others at my level here?" specific, comparative, addressable.
if the answer confirms the gap: you have something to work on. that's useful.
if the answer surprises you ("you're actually stronger than you think in that area"): that's data that what you're feeling might be more syndrome than gap.
both are workable. the mistake is treating them the same.