Question 4

Which of following statements is/are true?

Answer:
  • Indexes can solve the problem of slow queries - True
  • Indexes are fast to search because they're ordered such that you can find target values with few comparisons - True
  • Under heavy write load you should scale your read throughput by reading from secondaries - False since writes are replicated to secondaries all members of the replica set have about the same write workload therefore sending reads to a secondary will not scale you read throughput.
  • When you index on a field that is an array it creates a partial index - False since when you index a field that is an array it creates a multikey index.
  • On a sharded cluster, aggregation queries using $lookup will require a merge stage on a random shard - False. $lookup, $graphLookup, $facet, and $out all require a merge stage on the primary shard, not a random shard like most other merged queries.





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