[codingdave]

Does it work as expected? Then they did it correctly. Did they do it fast enough to meet the business needs? Then they did it quickly enough. Do they keep delivering things that work, that are done fast enough for the business, and you don't they keep working? Then the quality is high enough.

Trust your people. If you spend all your energy trying to second-guess whether they are competent, they won't stick with you. And if they did not deserve that trust, it will show in their results quickly enough anyway.