Read-Point Planning: Your Backlog Is a Cache of Beliefs Cache invalidation is famously one of the two hard things in computer science. The joke survives because the pain is real: keep a copy of something, and the moment the original changes, your copy starts lying to you. It lies silently, with a straight face, and it lies hardest to the people who trust it most. Here is the uncomfortable part. You are operating a large cache right now, and you are not invalidating it at all. It is called...