Databricks Certified Data Analyst Associate free question 6 / 10 · Domain 5: Analyzing Queries
A team runs two kinds of queries. Lookup queries each finish in under a second, and a nightly report scans several terabytes and runs for about 40 minutes. According to the Photon page, where does Photon give the greatest benefit?
- The sub-second lookups, because Photon cuts down their planning and scheduling time.
- Both alike, because Photon speeds up each query by about the same factor.
- The 40-minute report, because Photon helps most on long queries over large data.
- Neither, because Photon accelerates writes such as MERGE rather than reads.
Show the answer and explanation
Answer: C
Why this is correct
The Photon page says Photon provides the greatest benefit for longer-running queries that process large datasets. It processes data in columnar batches of thousands of rows, uses SIMD instructions in native C++, and replaces sort-merge joins with hash joins, all of which pay off when a query spends its time processing data. Queries that normally complete in under two seconds do not see meaningful improvement, because their execution time is dominated by planning and scheduling overhead rather than data processing. The 40-minute report is the workload that gains.
Why the other options are wrong
"The sub-second lookups, because Photon cuts down their planning and scheduling time." … Planning and scheduling are exactly the part Photon does not change: the Apache Spark optimizer still plans the query and Photon works at the execution layer. For queries under two seconds, that overhead dominates, so the page says they see no meaningful improvement.
"Both alike, because Photon speeds up each query by about the same factor." … The page does not describe a uniform speed-up. It says Photon provides the greatest benefit for longer-running queries that process large datasets, and that queries finishing in under two seconds do not see meaningful improvement.
"Neither, because Photon accelerates writes such as MERGE rather than reads." … Photon is described as a vectorized query engine that accelerates SQL workloads, DataFrame API calls, ETL pipelines and stateless streaming. Its scan efficiency features (filter pushdown, dictionary pruning, row-group skipping) speed up reads as well as writes.
Where Photon is already on
Photon is the default engine for all SQL warehouses, powering dashboards, ad hoc queries and scheduled reports, so analysts do not change their SQL to use it. The page also lists Photon among the limitations for very short queries: it does not improve queries that normally run in under two seconds.