In my experience at previous employment there were a lot of chancers in technical contracting for Java and front-end dev in London.

They all interview well, but when on the ground and asked to do stuff they are usually found out to be useless fairly quickly.

The "one weird trick companies dont want you to know!" is that it takes about a week or two for people to fully appreciate the contractor is useless and needs to be sacked, by which point they've made £500/day over a week or two which is £2500-5000 for half a month's effort which for a majority of people in London is a pretty tidy sum.

My lesson learnt from this is dont just quiz people in a face-to-face interview, but get them to do something in the interview.

Contractor in London here. I've seen this for Python / dev-ops as well, well more the aftermath since the contractors were usually already gone. But the level of incompetence was jarring for someone on 500 pounds per day (this was before Brexit).

Remember the people in these examples have been employed in the industry for years. You'll probably be working either alongside them or on the code they produced...