← Learn/Part 4 · Data engineering

The store accepts payments — a mistake here costs money. Transactions make a group of operations "all or nothing", and isolation levels protect against the chaos of concurrent access. The topic is conceptual: concurrency can't be fully shown with a single connection in the sandbox, so some lessons are theory with a quiz, while the practical ones work with BEGIN…COMMIT/ROLLBACK scenarios and a check of the final state of the data.