Performance (N+1 & DataLoader) interview questions

18 Performance (N+1 & DataLoader) questions from the GraphQL bank, written for Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd.

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1. What is N+1 problem?

Junior
  1. A.the inefficiency where resolving a list triggers one backend call per item plus the initial list fetch
  2. B.a per-request utility that batches and caches backend key lookups within a single tick to eliminate redundant fetches
  3. C.an optimization sending a hash instead of the full document, with the server caching the text after a first registration
  4. D.the short-lived memoization of loaded keys, scoped to one operation, that dedupes repeat lookups for the same id

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2. Which term means: "the inefficiency where resolving a list triggers one backend call per item plus the initial list fetch"?

Junior
  1. A.Batching
  2. B.DataLoader
  3. C.N+1 problem
  4. D.Automatic persisted queries

Answer + AI explanation with Pro

3. Which statement is correct?

Junior
  1. A.N+1 problem — collapsing many individual same-type key lookups gathered in one event-loop tick into a single backend request
  2. B.N+1 problem — an optimization sending a hash instead of the full document, with the server caching the text after a first registration
  3. C.N+1 problem — the inefficiency where resolving a list triggers one backend call per item plus the initial list fetch
  4. D.N+1 problem — the short-lived memoization of loaded keys, scoped to one operation, that dedupes repeat lookups for the same id

Answer + AI explanation with Pro

4. What is DataLoader?

Mid
  1. A.collapsing many individual same-type key lookups gathered in one event-loop tick into a single backend request
  2. B.a per-request utility that batches and caches backend key lookups within a single tick to eliminate redundant fetches
  3. C.the short-lived memoization of loaded keys, scoped to one operation, that dedupes repeat lookups for the same id
  4. D.an optimization sending a hash instead of the full document, with the server caching the text after a first registration

Answer + AI explanation with Pro

5. Which term means: "a per-request utility that batches and caches backend key lookups within a single tick to eliminate redundant fetches"?

Mid
  1. A.Batching
  2. B.Per-request cache
  3. C.DataLoader
  4. D.N+1 problem

Answer + AI explanation with Pro

6. Which statement is correct?

Mid
  1. A.DataLoader — scoring a document's cost before execution to reject overly expensive or deeply nested requests
  2. B.DataLoader — an optimization sending a hash instead of the full document, with the server caching the text after a first registration
  3. C.DataLoader — the short-lived memoization of loaded keys, scoped to one operation, that dedupes repeat lookups for the same id
  4. D.DataLoader — a per-request utility that batches and caches backend key lookups within a single tick to eliminate redundant fetches

Answer + AI explanation with Pro

7. What is Batching?

Mid
  1. A.collapsing many individual same-type key lookups gathered in one event-loop tick into a single backend request
  2. B.scoring a document's cost before execution to reject overly expensive or deeply nested requests
  3. C.the inefficiency where resolving a list triggers one backend call per item plus the initial list fetch
  4. D.an optimization sending a hash instead of the full document, with the server caching the text after a first registration

Answer + AI explanation with Pro

8. Which term means: "collapsing many individual same-type key lookups gathered in one event-loop tick into a single backend request"?

Mid
  1. A.Automatic persisted queries
  2. B.Batching
  3. C.DataLoader
  4. D.N+1 problem

Answer + AI explanation with Pro

9. Which statement is correct?

Mid
  1. A.Batching — the short-lived memoization of loaded keys, scoped to one operation, that dedupes repeat lookups for the same id
  2. B.Batching — collapsing many individual same-type key lookups gathered in one event-loop tick into a single backend request
  3. C.Batching — a per-request utility that batches and caches backend key lookups within a single tick to eliminate redundant fetches
  4. D.Batching — the inefficiency where resolving a list triggers one backend call per item plus the initial list fetch

Answer + AI explanation with Pro

10. What is Per-request cache?

Mid
  1. A.a per-request utility that batches and caches backend key lookups within a single tick to eliminate redundant fetches
  2. B.the short-lived memoization of loaded keys, scoped to one operation, that dedupes repeat lookups for the same id
  3. C.scoring a document's cost before execution to reject overly expensive or deeply nested requests
  4. D.collapsing many individual same-type key lookups gathered in one event-loop tick into a single backend request

Answer + AI explanation with Pro

11. Which term means: "the short-lived memoization of loaded keys, scoped to one operation, that dedupes repeat lookups for the same id"?

Mid
  1. A.Query complexity analysis
  2. B.Batching
  3. C.N+1 problem
  4. D.Per-request cache

Answer + AI explanation with Pro

12. Which statement is correct?

Mid
  1. A.Per-request cache — a per-request utility that batches and caches backend key lookups within a single tick to eliminate redundant fetches
  2. B.Per-request cache — an optimization sending a hash instead of the full document, with the server caching the text after a first registration
  3. C.Per-request cache — the short-lived memoization of loaded keys, scoped to one operation, that dedupes repeat lookups for the same id
  4. D.Per-request cache — collapsing many individual same-type key lookups gathered in one event-loop tick into a single backend request

Answer + AI explanation with Pro

13. What is Query complexity analysis?

Senior
  1. A.an optimization sending a hash instead of the full document, with the server caching the text after a first registration
  2. B.collapsing many individual same-type key lookups gathered in one event-loop tick into a single backend request
  3. C.the short-lived memoization of loaded keys, scoped to one operation, that dedupes repeat lookups for the same id
  4. D.scoring a document's cost before execution to reject overly expensive or deeply nested requests

Answer + AI explanation with Pro

14. Which term means: "scoring a document's cost before execution to reject overly expensive or deeply nested requests"?

Senior
  1. A.DataLoader
  2. B.N+1 problem
  3. C.Per-request cache
  4. D.Query complexity analysis

Answer + AI explanation with Pro

15. Which statement is correct?

Senior
  1. A.Query complexity analysis — a per-request utility that batches and caches backend key lookups within a single tick to eliminate redundant fetches
  2. B.Query complexity analysis — scoring a document's cost before execution to reject overly expensive or deeply nested requests
  3. C.Query complexity analysis — the short-lived memoization of loaded keys, scoped to one operation, that dedupes repeat lookups for the same id
  4. D.Query complexity analysis — collapsing many individual same-type key lookups gathered in one event-loop tick into a single backend request

Answer + AI explanation with Pro

16. What is Automatic persisted queries?

Senior
  1. A.collapsing many individual same-type key lookups gathered in one event-loop tick into a single backend request
  2. B.an optimization sending a hash instead of the full document, with the server caching the text after a first registration
  3. C.scoring a document's cost before execution to reject overly expensive or deeply nested requests
  4. D.the short-lived memoization of loaded keys, scoped to one operation, that dedupes repeat lookups for the same id

Answer + AI explanation with Pro

17. Which term means: "an optimization sending a hash instead of the full document, with the server caching the text after a first registration"?

Senior
  1. A.DataLoader
  2. B.Per-request cache
  3. C.Automatic persisted queries
  4. D.N+1 problem

Answer + AI explanation with Pro

18. Which statement is correct?

Senior
  1. A.Automatic persisted queries — scoring a document's cost before execution to reject overly expensive or deeply nested requests
  2. B.Automatic persisted queries — collapsing many individual same-type key lookups gathered in one event-loop tick into a single backend request
  3. C.Automatic persisted queries — an optimization sending a hash instead of the full document, with the server caching the text after a first registration
  4. D.Automatic persisted queries — the inefficiency where resolving a list triggers one backend call per item plus the initial list fetch

Answer + AI explanation with Pro

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