Question

A data engineering team runs a streaming job that continuously appends records to a Delta table while an analyst simultaneously runs a large aggregation query against the same table. The analyst is concerned that they might read a mix of old and newly written data mid-transaction, producing inconsistent results. Which characteristic of Delta Lake ensures the analyst's query returns consistent results?

Accepted Answer

Delta Lake provides snapshot isolation via the transaction log, so the read query sees a consistent version of the table as of the moment the query started.

Answer

Delta Lake locks the entire table during writes, blocking all read queries until the append completes.

Answer

Delta Lake automatically pauses the streaming write whenever a read query begins to avoid conflicts.

Answer

Delta Lake caches the query result in memory so the analyst never reads directly from the underlying files.