Designing Delta Table Contracts

Delta Lake table contracts start with a simple promise: every downstream job should know what columns exist, how fresh the data is, who owns the table, and what version was used for an important model or report.

What the contract captures

• Schema: required columns, nullable fields, generated columns, and known evolution rules.
• Freshness: expected update cadence and alert thresholds.
• Ownership: the team that approves breaking changes.
• History: how consumers can inspect table versions and recover from bad writes.

Example review query

DESCRIBE HISTORY main.features.customer_features;

SELECT
  max(event_time) AS latest_event,
  count(*) AS rows_written
FROM main.features.customer_features
WHERE event_date = current_date();

Rule of thumb

If a model uses a table, the table is no longer just storage. It is an interface. Treat its schema, freshness, and lineage as part of the model system.