Data Contract

A data contract is a formal agreement between a data producer (a team, service, or API) and its consumers that defines the schema, semantics, quality guarantees, and SLAs for the data being provided. It makes implicit assumptions explicit and versioned.

A data contract might specify: the exact field names and types in a dataset, the maximum null rate for critical fields, the expected freshness of records, and the change policy (breaking changes require 30 days notice and a new contract version). This prevents producers from changing data in ways that silently break consumers.

Data contracts are a relatively new practice in data engineering, emerging as a solution to the 'silent breaking change' problem that plagues large data platforms with many teams sharing pipelines. Tools like Great Expectations, Soda, and custom schema registries are used to encode and enforce data contracts automatically.