We’re a very small team with little experience in hiring but got approval for a new engineer. Basically HR will look for people through the usual channels and I think we have a reasonably good job description. Unfortunately the coding challenge (a 30h+ take home) is atrociously difficult and doesn’t really reflect what we do. On the other hand I think the false positive rate would be low. FWIW it’s a Linux application and it might be difficult to only count on experience from the CV.
Any ideas how to build a good challenge from scratch and what time constraints are reasonable?
Short answer: don’t. Ask questions that demonstrate familiarity with concepts that you and your team encounter in a regular basis.
If you insist on a coding challenge, give them an old but difficult problem your team encountered in the job and assess how they would solve it.