Delta Lake adds reliability to data lakes:
ACID transactions: Multiple writers can update the same table safely. No more corrupted data from failed jobs.
Schema enforcement: Delta rejects writes that don't match the table schema. Schema evolution is explicit.
Time travel: Query historical versions using version numbers or timestamps.
MERGE support: Upserts become simple:
MERGE INTO target USING source
ON target.id = source.id
WHEN MATCHED THEN UPDATE
WHEN NOT MATCHED THEN INSERT
Delta tables are just Parquet files plus a transaction log.