A **Base Search** runs once and feeds its results into multiple **Post-Process Searches**. Each post-process search applies additional transformations (stats, eval, where) without re-running the expensive base query.
This is a **critical** dashboard performance technique: instead of 10 panels each running the same base search, one base search feeds all 10.
In Simple XML, the base search has an `id`, and each post-process panel references it via `base="search_id"`.