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Databricks Certified Data Engineer Professional Practice Test 9

Question 80

At Granite Edge Labs, a regulated dataset must delete customer records after a documented retention period. A change is required because: Expired records remain available in historical serving tables. Which implementation action most directly corrects the configuration?

  1. Attach the supported row filter to the eligible table
  2. Apply deletes to eligible tables and update derived datasets as required
  3. Attach a supported mask function to the email column
  4. Execute authorized deletes and schedule supported retention-safe cleanup

Explanation

Correct Answer

D:

Execute authorized deletes and schedule supported retention-safe cleanup. This directly changes the feature or logic behind expired records remain available in historical serving tables. Retention design must remove records and account for Delta time travel and obsolete files. It is the concrete configuration for the stated incident.

Incorrect Answers

A:

Attach the supported row filter to the eligible table. This implement action addresses a different case (unity catalog row filter), where a shared table currently returns all regions to every reader. Unity Catalog row filters can restrict row visibility through governed policies. In the stated problem, expired records remain available in historical serving tables; this choice would not establish the required retention purge decision.

B:

Apply deletes to eligible tables and update derived datasets as required. This implement action addresses a different case (data subject request), where deleting a row from only the gold table leaves copies elsewhere. A complete delete workflow tracks identifiers and propagation across all governed copies. In the stated problem, expired records remain available in historical serving tables; this choice would not establish the required retention purge decision.

C:

Attach a supported mask function to the email column. This implement action addresses a different case (column masking), where a raw SELECT on an approved table exposes plaintext email. Unity Catalog column masks can transform sensitive values at read time. In the stated problem, expired records remain available in historical serving tables; this choice would not establish the required retention purge decision.

Question 81

Quality assurance at Lakewood Distribution checks a corrected workload where a filter on event_date scans nearly all Delta files. The original fault was: File-level statistics are missing for the filter column. Which verification is most decisive?

  1. Compare scanned files before and after on the same date predicate
  2. Run representative device filters and compare data skipping
  3. Reconcile rows and compare scan cost against text storage
  4. Reconcile changed rows and compare scanned file counts

Explanation

Correct Answer

A:

Compare scanned files before and after on the same date predicate. This tests the expected result against file-level statistics are missing for the filter column, not simply whether a job or object exists. Delta data skipping uses collected column statistics to eliminate files.

Incorrect Answers

B:

Run representative device filters and compare data skipping. This validate action addresses a different case (liquid clustering cardinality), where partitioning by device would produce many tiny partitions. Liquid clustering organizes data by useful filter keys without high-cardinality partition directories. In the stated problem, file-level statistics are missing for the filter column; this choice would not establish the required data skipping statistics decision.

C:

Reconcile rows and compare scan cost against text storage. This validate action addresses a different case (columnar compression), where row-oriented text storage increases scans and transfer volumes. Columnar formats and appropriate encoding improve analytical read efficiency. In the stated problem, file-level statistics are missing for the filter column; this choice would not establish the required data skipping statistics decision.

D:

Reconcile changed rows and compare scanned file counts. This validate action addresses a different case (predicate-limited merge), where the merge scans unrelated historical partitions. Constraining merge matches to relevant partitions can reduce unnecessary target scanning. In the stated problem, file-level statistics are missing for the filter column; this choice would not establish the required data skipping statistics decision.

Question 82

At Granite Edge Labs, a Spark stream consumes from a Kafka topic into Delta. A change was deployed to address: Restarting with a fresh checkpoint replays previously ingested messages. Which test result provides the strongest evidence that the requirement is now met?

  1. Append one new object and verify it is ingested only once
  2. Restart the job and verify no duplicate committed records
  3. Ingest old and new samples and verify nested fields and rescued data are retained
  4. Deserialize old and new messages with the intended projection

Explanation

Correct Answer

B:

Restart the job and verify no duplicate committed records. This tests the expected result against restarting with a fresh checkpoint replays previously ingested messages, not simply whether a job or object exists. A stable streaming checkpoint maintains Kafka offsets and sink progress across restarts.

Incorrect Answers

A:

Append one new object and verify it is ingested only once. This validate action addresses a different case (auto loader file discovery), where listing the full historical directory every run exceeds the ingestion SLA. Auto Loader is designed for incremental new-file discovery with persisted state. In the stated problem, restarting with a fresh checkpoint replays previously ingested messages; this choice would not establish the required kafka offset durability decision.

C:

Ingest old and new samples and verify nested fields and rescued data are retained. This validate action addresses a different case (nested json ingest), where the initial reader assumes one unchanging flat schema and loses new fields. Explicit schema management and rescued data handling protect evolving semi-structured ingestion. In the stated problem, restarting with a fresh checkpoint replays previously ingested messages; this choice would not establish the required kafka offset durability decision.

D:

Deserialize old and new messages with the intended projection. This validate action addresses a different case (avro schema evolution), where an older consumer cannot deserialize records from a newer producer schema. Avro writer-reader schema compatibility must be maintained for evolution. In the stated problem, restarting with a fresh checkpoint replays previously ingested messages; this choice would not establish the required kafka offset durability decision.

Question 83

At Clearstone Media, a product dimension adds a new optional classification attribute. A change was deployed to address: A destructive table recreation would invalidate downstream consumers. Which test result provides the strongest evidence that the requirement is now met?

  1. Query facts as of past dates and verify the appropriate historical tier
  2. Join reports across marts and verify consistent country totals
  3. Query old and new rows and confirm existing measures and keys remain valid
  4. Inject malformed input and confirm it never contaminates gold

Explanation

Correct Answer

C:

Query old and new rows and confirm existing measures and keys remain valid. This tests the expected result against a destructive table recreation would invalidate downstream consumers, not simply whether a job or object exists. Additive schema evolution can preserve contracts when null defaults are acceptable.

Incorrect Answers

A:

Query facts as of past dates and verify the appropriate historical tier. This validate action addresses a different case (scd type 2 effective dates), where a single current tier overwrites history in the dimension. SCD Type 2 stores effective start/end intervals for distinct historical dimension versions. In the stated problem, a destructive table recreation would invalidate downstream consumers; this choice would not establish the required dimension evolution decision.

B:

Join reports across marts and verify consistent country totals. This validate action addresses a different case (conformed dimensions), where the same country appears under conflicting dimension keys across marts. A conformed dimension provides common attribute definitions across fact models. In the stated problem, a destructive table recreation would invalidate downstream consumers; this choice would not establish the required dimension evolution decision.

D:

Inject malformed input and confirm it never contaminates gold. This validate action addresses a different case (medallion bronze silver gold), where malformed source events contaminate metrics without an intermediate quality boundary. Bronze, silver and gold layers separate raw capture, validated refinement and business presentation. In the stated problem, a destructive table recreation would invalidate downstream consumers; this choice would not establish the required dimension evolution decision.

Question 84

A data engineer at Westhaven Services must troubleshoot this case: a daily Delta MERGE updates a tiny set of dates in a massive fact table. Evidence: The merge scans unrelated historical partitions. What should be inspected first to confirm the failure mechanism?

  1. Inspect current table features, delete patterns and runtime compatibility
  2. Inspect filters, cardinalities and existing partition layout
  3. Inspect schema, compression ratio and scan bytes for current storage
  4. Inspect MERGE condition and target files read

Explanation

Correct Answer

D:

Inspect MERGE condition and target files read. This checks the specific evidence behind the merge scans unrelated historical partitions. Constraining merge matches to relevant partitions can reduce unnecessary target scanning. The investigation distinguishes the mechanism from an unrelated operational symptom.

Incorrect Answers

A:

Inspect current table features, delete patterns and runtime compatibility. This diagnose action addresses a different case (deletion vectors), where each small delete rewrites large data files and increases write cost. Deletion vectors can mark deleted rows without immediate whole-file rewrite when supported. In the stated problem, the merge scans unrelated historical partitions; this choice would not establish the required predicate-limited merge decision.

B:

Inspect filters, cardinalities and existing partition layout. This diagnose action addresses a different case (liquid clustering cardinality), where partitioning by device would produce many tiny partitions. Liquid clustering organizes data by useful filter keys without high-cardinality partition directories. In the stated problem, the merge scans unrelated historical partitions; this choice would not establish the required predicate-limited merge decision.

C:

Inspect schema, compression ratio and scan bytes for current storage. This diagnose action addresses a different case (columnar compression), where row-oriented text storage increases scans and transfer volumes. Columnar formats and appropriate encoding improve analytical read efficiency. In the stated problem, the merge scans unrelated historical partitions; this choice would not establish the required predicate-limited merge decision.

Question 85

At Cobalt Biotech, a bronze layer ingests immutable audit event files. The known risk is: A nightly overwrite accidentally removes historical audit events. After remediation, which ongoing signal best detects recurrence?

  1. Monitor unexpected overwrite or delete operations on bronze
  2. Monitor discovered-file backlog and ingestion freshness
  3. Monitor unexpected file sizes and unsupported media types
  4. Alert when rescued-data volume rises after schema changes

Explanation

Correct Answer

A:

Monitor unexpected overwrite or delete operations on bronze. This watches the failure mode described by a nightly overwrite accidentally removes historical audit events. Append-only ingestion keeps previous raw records while adding new batches. It supplies a regression signal after remediation.

Incorrect Answers

B:

Monitor discovered-file backlog and ingestion freshness. This monitor action addresses a different case (auto loader file discovery), where listing the full historical directory every run exceeds the ingestion SLA. Auto Loader is designed for incremental new-file discovery with persisted state. In the stated problem, a nightly overwrite accidentally removes historical audit events; this choice would not establish the required append-only delta bronze decision.

C:

Monitor unexpected file sizes and unsupported media types. This monitor action addresses a different case (binary payload metadata), where a line-oriented text reader corrupts the raw binary payload. binaryFile input preserves raw file bytes and path metadata rather than decoding lines. In the stated problem, a nightly overwrite accidentally removes historical audit events; this choice would not establish the required append-only delta bronze decision.

D:

Alert when rescued-data volume rises after schema changes. This monitor action addresses a different case (auto loader rescued data), where unknown or mismatched fields disappear during the bronze load. The rescued data column can preserve records with unexpected schema content for later remediation. In the stated problem, a nightly overwrite accidentally removes historical audit events; this choice would not establish the required append-only delta bronze decision.

Question 86

An architecture review at Summit Consumer Goods covers a workload where a large Delta table receives frequent narrow DELETE operations. The unresolved constraint is: Each small delete rewrites large data files and increases write cost. Which design is most appropriate?

  1. Use predictive optimization on supported managed Delta tables
  2. Enable supported deletion vectors for selective mutation workloads
  3. Choose a supported columnar Delta or Parquet layout for analytics
  4. Schedule appropriate compaction or predictive optimization for the table

Explanation

Correct Answer

B:

Enable supported deletion vectors for selective mutation workloads. This design addresses each small delete rewrites large data files and increases write cost. Deletion vectors can mark deleted rows without immediate whole-file rewrite when supported. It establishes the right contract or architecture before execution changes.

Incorrect Answers

A:

Use predictive optimization on supported managed Delta tables. This design action addresses a different case (predictive optimization), where operators run blanket manual OPTIMIZE jobs regardless of table use. Predictive optimization can automate supported managed-table maintenance based on workload signals. In the stated problem, each small delete rewrites large data files and increases write cost; this choice would not establish the required deletion vectors decision.

C:

Choose a supported columnar Delta or Parquet layout for analytics. This design action addresses a different case (columnar compression), where row-oriented text storage increases scans and transfer volumes. Columnar formats and appropriate encoding improve analytical read efficiency. In the stated problem, each small delete rewrites large data files and increases write cost; this choice would not establish the required deletion vectors decision.

D:

Schedule appropriate compaction or predictive optimization for the table. This design action addresses a different case (small file compaction), where read overhead grows because query plans open excessive small files. OPTIMIZE can compact compatible Delta files without changing logical table contents. In the stated problem, each small delete rewrites large data files and increases write cost; this choice would not establish the required deletion vectors decision.

Question 87

Quality assurance at Riverbend Energy checks a corrected workload where two data science teams must join events without exposing raw customer IDs. The original fault was: A naive hash without controlled key management risks predictable identifiers. Which verification is most decisive?

  1. Confirm totals match while customer identifiers cannot be queried
  2. Confirm reader cannot edit but approved maintainer can deploy
  3. Confirm equal source IDs map to equal pseudonyms without exposing originals
  4. Trigger a test error and confirm logs reveal no PII content

Explanation

Correct Answer

C:

Confirm equal source IDs map to equal pseudonyms without exposing originals. This tests the expected result against a naive hash without controlled key management risks predictable identifiers, not simply whether a job or object exists. Keyed pseudonymization can preserve joins while reducing identifier exposure.

Incorrect Answers

A:

Confirm totals match while customer identifiers cannot be queried. This validate action addresses a different case (secure view sharing), where granting SELECT on the raw fact table violates minimization. A governed aggregation view can expose only approved derived information. In the stated problem, a naive hash without controlled key management risks predictable identifiers; this choice would not establish the required pseudonymized join keys decision.

B:

Confirm reader cannot edit but approved maintainer can deploy. This validate action addresses a different case (workspace object acl), where the team needs read-only access for most users. Workspace object permissions can restrict who can edit or manage shared code. In the stated problem, a naive hash without controlled key management risks predictable identifiers; this choice would not establish the required pseudonymized join keys decision.

D:

Trigger a test error and confirm logs reveal no PII content. This validate action addresses a different case (restricted event logging), where logs expose PII to broader operations readers. Logging should redact or omit sensitive payload fields while preserving diagnostic codes. In the stated problem, a naive hash without controlled key management risks predictable identifiers; this choice would not establish the required pseudonymized join keys decision.

Question 88

Operations at Redwood Civic Services owns a workload where an upstream producer starts adding optional nested JSON fields to order events. The previously identified issue was: The initial reader assumes one unchanging flat schema and loses new fields. Which metric or audit check best detects drift?

  1. Monitor missing child-element and parser error counts
  2. Monitor malformed CSV rows and supplier format drift
  3. Monitor newly arriving file-schema mismatches
  4. Monitor schema changes and rescued-field counts

Explanation

Correct Answer

D:

Monitor schema changes and rescued-field counts. This watches the failure mode described by the initial reader assumes one unchanging flat schema and loses new fields. Explicit schema management and rescued data handling protect evolving semi-structured ingestion. It supplies a regression signal after remediation.

Incorrect Answers

A:

Monitor missing child-element and parser error counts. This monitor action addresses a different case (xml repeating elements), where an XML ingest incorrectly flattens multiple line items into one text field. XML ingestion must specify the repeating row element and preserve nested structure. In the stated problem, the initial reader assumes one unchanging flat schema and loses new fields; this choice would not establish the required nested json ingest decision.

B:

Monitor malformed CSV rows and supplier format drift. This monitor action addresses a different case (malformed csv quotes), where an ingestion reader splits quoted names into extra columns. CSV quoting and escape configurations must match the source serialization. In the stated problem, the initial reader assumes one unchanging flat schema and loses new fields; this choice would not establish the required nested json ingest decision.

C:

Monitor newly arriving file-schema mismatches. This monitor action addresses a different case (parquet schema mismatch), where a merge step fails after a producer changes an integer field to string. Parquet schema compatibility matters even when column names are unchanged. In the stated problem, the initial reader assumes one unchanging flat schema and loses new fields; this choice would not establish the required nested json ingest decision.

Question 89

At Arbor Medical, short scheduled ETL tasks waste time starting and idling classic clusters. The known risk is: Provisioning overhead exceeds useful task execution time. After remediation, which ongoing signal best detects recurrence?

  1. Monitor serverless task failures and cost per run
  2. Monitor cache hit rate and eviction pressure
  3. Monitor shuffle size per task and batch runtime
  4. Monitor optimization operations and cost savings

Explanation

Correct Answer

A:

Monitor serverless task failures and cost per run. This watches the failure mode described by provisioning overhead exceeds useful task execution time. Supported serverless jobs can reduce infrastructure management and startup overhead. It supplies a regression signal after remediation.

Incorrect Answers

B:

Monitor cache hit rate and eviction pressure. This monitor action addresses a different case (cache reuse), where repeated recomputation dominates each branch's execution. Persistence can avoid repeated work if reused data fits the memory budget. In the stated problem, provisioning overhead exceeds useful task execution time; this choice would not establish the required serverless job fit decision.

C:

Monitor shuffle size per task and batch runtime. This monitor action addresses a different case (shuffle partition count), where the current partition count is too low for data volume. Shuffle partition sizing affects memory pressure and task parallelism. In the stated problem, provisioning overhead exceeds useful task execution time; this choice would not establish the required serverless job fit decision.

D:

Monitor optimization operations and cost savings. This monitor action addresses a different case (predictive optimization), where operators run blanket manual OPTIMIZE jobs regardless of table use. Predictive optimization can automate supported managed-table maintenance based on workload signals. In the stated problem, provisioning overhead exceeds useful task execution time; this choice would not establish the required serverless job fit decision.

Question 90

At Cascade Manufacturing, compliance needs to identify all tables containing restricted PII. The known risk is: Naming conventions alone are inconsistent across teams. After remediation, which ongoing signal best detects recurrence?

  1. Audit unapproved external paths and location changes
  2. Audit tag removal or changes to sensitive labels
  3. Audit subsequent data access requests and grants
  4. Audit new location definitions and path overlaps

Explanation

Correct Answer

B:

Audit tag removal or changes to sensitive labels. This watches the failure mode described by naming conventions alone are inconsistent across teams. Governed tags can classify assets for discovery and policy workflows. It supplies a regression signal after remediation.

Incorrect Answers

A:

Audit unapproved external paths and location changes. This monitor action addresses a different case (managed storage ownership), where the data platform cannot apply consistent lifecycle governance. Managed locations centralize storage ownership for Unity Catalog managed assets. In the stated problem, naming conventions alone are inconsistent across teams; this choice would not establish the required governed tags decision.

C:

Audit subsequent data access requests and grants. This monitor action addresses a different case (browse metadata privilege), where teams grant SELECT merely to expose object listings. BROWSE enables controlled metadata discovery without granting data read access. In the stated problem, naming conventions alone are inconsistent across teams; this choice would not establish the required governed tags decision.

D:

Audit new location definitions and path overlaps. This monitor action addresses a different case (external location governance), where raw cloud permissions bypass central catalog governance. External locations map cloud paths to governed Unity Catalog storage credentials. In the stated problem, naming conventions alone are inconsistent across teams; this choice would not establish the required governed tags decision.

Certified Data Engineer Professional Practice Tests