MongoDB DBA Performance Monitoring Quiz

1. What does 'working set' refer to in MongoDB performance monitoring?

All documents in a collection

Data frequently accessed by queries

Indexes stored in memory

Temporary query results

2. Which profiler level captures all operations including reads and writes?

Level 0

Level 1

Level 2

Level 3

3. What does the 'allPlans' field in explain() output contain?

All possible query execution plans considered

All indexes available on the collection

All documents matching the query

All replication plans for the cluster

4. How can you reduce memory consumption on a MongoDB server?

Disable all indexes

Remove unused indexes and optimize working set

Reduce the number of connections

Disable the profiler completely

5. What does 'index cardinality' measure in MongoDB?

The size of the index file

The number of unique values in indexed field

The number of documents indexed

The order of index creation

6. Which tool provides visual query performance analysis in MongoDB?

MongoDB Shell

MongoDB Compass

MongoDB Atlas

MongoDB Connector

7. What is the significance of 'nReturned' versus 'totalDocsExamined' in explain()?

They are always equal in efficient queries

Large difference indicates inefficient index usage

NReturned is always larger

TotalDocsExamined is irrelevant for performance

8. How do you view the currently active operations in MongoDB?

Db.currentOp()

Db.listOperations()

Db.getActiveQueries()

Db.showOperations()

9. What does the 'stage' field in explain() output describe?

The database version being used

Steps the query engine takes to retrieve documents

The replication stage of the cluster

The backup stage of data

10. Which index type is optimal for geospatial queries in MongoDB?

Compound index

Text index

Geospatial 2dsphere index

Unique index

11. Which MongoDB tool provides real-time performance metrics and resource usage information?

MongoDB Compass

MongoDB Atlas Charts

MongoDB Ops Manager

MongoDB Shell

12. Which MongoDB feature helps identify slow queries automatically?

Query Cache

Profiler and slow query log

Connection pooling

Aggregation framework

13. What is the 'executionTimeMillis' value used for in performance analysis?

Measuring query planning time only

Measuring total execution time of the query

Measuring network latency

Measuring index creation time

14. How should you design indexes to support queries with multiple field conditions?

Create separate single-field indexes for each field

Use compound indexes matching query patterns

Always use text indexes

Avoid indexes on conditional fields

15. Which monitoring metric tracks the percentage of available memory consumed?

CPU utilization

Memory resident set size (RSS)

Disk queue depth

Network throughput

16. What does COLLSCAN mean in MongoDB query execution?

Collection scan using an index

Full collection scan without index

Clustered collection scan

Conditional logical scan

17. Which metric in explain() output indicates how many documents were examined to return results?

ExecutionStages.nReturned

ExecutionStages.totalDocsExamined

ExecutionStats.scannedObjects

QueryPlanner.winningPlan

18. What is the primary purpose of creating compound indexes in MongoDB?

Reduce storage requirements

Support queries on multiple fields efficiently

Improve write performance only

Eliminate the need for query optimization

19. Which command enables query profiling on the current database?

Db.setProfilingLevel()

Db.enableProfiler()

Db.startProfiling()

Db.activateProfiler()

20. What does the profiler level 1 in MongoDB capture?

All database operations

Only slow operations exceeding the threshold

Only read operations

Administrative commands only