Why it matters

Delta Lake makes data lakes reliable. Understanding shapes production data pipelines.

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The architecture

Delta format: Parquet files + JSON transaction log.

Log records every commit atomically.

Delta Lake structureParquet datacolumnar filesTransaction logJSON append-onlyReader combinesconsistent snapshotConcurrent writers use optimistic concurrency; log provides serializability
Delta storage model.
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How it works end to end

ACID: writes atomic via log. Reads snapshot-isolated.

Time travel: query old versions via VERSION AS OF or TIMESTAMP AS OF.

Schema evolution: add columns, rename with care.

MERGE / UPDATE / DELETE: like SQL DB.