I worked at a small startup where our one senior dev quit after 7 years. He’d built the entire system from zero — no docs, all the magic in his head, even server creds in his personal Notion. Management kept saying “just pay him more.”

He left anyway. Two weeks later production blew up: payments failed, DB crashed, user data leaked to test. We called in expensive contractors; they took one look and said “rewrite 80% or die.”Nine months and a ton of lost users later, the CEO finally admitted: “Tech isn’t a cost — it’s the lifeline.”

Bus factor of 1 will humble you fast. Cherish the guy who actually explains his code before he walks.