Well, hopefully they: * Are good at documenting * Communicate what and why they chose it during code reviews * Encapsulate their work behind sensible functio

Well, hopefully they: * Are good at documenting * Communicate what and why they chose it during code reviews * Encapsulate their work behind sensible functions/APIs that don't require intimate knowledge of complex internals And if they aren't, that's worth bringing up to them. If it's still a problem it's worth bringing up to your team/project lead or otherwise.