The needs: keyword enables executing jobs out-of-order, allowing you to implement a directed acyclic graph in your .gitlab-ci.yml. This lets you run some jobs without waiting for other ones, disregarding stage ordering so you can have multiple stages running concurrently.

A spreadsheet may be represented as a directed acyclic graph, with each cell a vertex and an edge connected a cell when a formula references another cell. Other applications include scheduling, circuit design and Bayesian networks.