At my last company, I joined as their lead developer and discovered they already had another developer in the pipeline they were thinking of hiring. They thought the guy was super senior, and when I read his CV sure enough he came across that way. He emphasized on his CV that he was not only a Java expert but an expert on the internals of HotSpot itself.
Probably he'd been saying that for years, and given how many firms use the JVM it's probably a great line. Unlucky for him he got an interviewer (me) who actually was an expert in the HotSpot internals and liked to relax by reading its source code. Guess what? He knew nothing about the JVM, not even stuff you'd learn by reading the user guide. I got the sense he'd read one or two popular press articles about it 20 years ago, put it on his CV and never updated it.
So we progress to some coding. He can't code. He struggles with even the basics of starting a new program in an editor and compiling it.
The guy was demanding a huuuge salary and great perks. After I wrote up what I'd found from the coding interview he was quietly dropped from the pipeline. They'd been about to accept because they were so dazzled by his claims but weren't checking them.
The "knew it once maybe sorta" problem is common, especially with C++ where lots of people were struggling with it in the 90s and then jumped to Java/C# as soon as they came out. But they still list C++ on their CV. Ask them to write a C++ program (that does anything at all) and they'll just refuse or state point blank they'd feel really uncomfortable doing that.
Lots of people lie about their experience unfortunately. They probably don't think of it as lying. They just write down every possible thing they've ever thought or read about and exaggerate, gambling that they'll never be called on it. And, they're probably right. That's why coding interviews took off.
