21 Data Structures questions from the Redis 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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A.the most basic Redis value type, a binary-safe sequence of bytes up to 512 MB holding text, numbers, or serialized objects
B.a probabilistic structure that estimates the cardinality of a large set using roughly 12 KB regardless of element count, with about 0.81% standard error
C.an append-only log of entries with unique ids, supporting time-ordered reads, ranges, and consumer groups for messaging workloads
D.a collection of unique members each ordered by an associated floating-point score, enabling fast range and rank queries
Answer + AI explanation with Pro
2. Which term means: "the most basic Redis value type, a binary-safe sequence of bytes up to 512 MB holding text, numbers, or serialized objects"?
Junior
A.Stream
B.List
C.String
D.Hash
Answer + AI explanation with Pro
3. Which statement is correct?
Junior
A.String — an append-only log of entries with unique ids, supporting time-ordered reads, ranges, and consumer groups for messaging workloads
B.String — an ordered sequence of entries implemented as a linked structure where pushes and pops at either end run in constant time
C.String — a value type mapping field names to values, ideal for representing a single object with many attributes compactly
D.String — the most basic Redis value type, a binary-safe sequence of bytes up to 512 MB holding text, numbers, or serialized objects
Answer + AI explanation with Pro
4. What is List?
Junior
A.the most basic Redis value type, a binary-safe sequence of bytes up to 512 MB holding text, numbers, or serialized objects
B.a value type mapping field names to values, ideal for representing a single object with many attributes compactly
C.an ordered sequence of entries implemented as a linked structure where pushes and pops at either end run in constant time
D.a probabilistic structure that estimates the cardinality of a large set using roughly 12 KB regardless of element count, with about 0.81% standard error
Answer + AI explanation with Pro
5. Which term means: "an ordered sequence of entries implemented as a linked structure where pushes and pops at either end run in constant time"?
Junior
A.Stream
B.Bitmap
C.List
D.Sorted set
Answer + AI explanation with Pro
6. Which statement is correct?
Junior
A.List — an extension of the string type letting you set, clear, and count individual bits by offset, perfect for compact boolean flags per id
B.List — an ordered sequence of entries implemented as a linked structure where pushes and pops at either end run in constant time
C.List — a collection of unique members each ordered by an associated floating-point score, enabling fast range and rank queries
D.List — an append-only log of entries with unique ids, supporting time-ordered reads, ranges, and consumer groups for messaging workloads
Answer + AI explanation with Pro
7. What is Hash?
Junior
A.the most basic Redis value type, a binary-safe sequence of bytes up to 512 MB holding text, numbers, or serialized objects
B.an extension of the string type letting you set, clear, and count individual bits by offset, perfect for compact boolean flags per id
C.a value type mapping field names to values, ideal for representing a single object with many attributes compactly
D.an ordered sequence of entries implemented as a linked structure where pushes and pops at either end run in constant time
Answer + AI explanation with Pro
8. Which term means: "a value type mapping field names to values, ideal for representing a single object with many attributes compactly"?
Junior
A.Hash
B.Bitmap
C.HyperLogLog
D.Sorted set
Answer + AI explanation with Pro
9. Which statement is correct?
Junior
A.Hash — an ordered sequence of entries implemented as a linked structure where pushes and pops at either end run in constant time
B.Hash — a probabilistic structure that estimates the cardinality of a large set using roughly 12 KB regardless of element count, with about 0.81% standard error
C.Hash — a value type mapping field names to values, ideal for representing a single object with many attributes compactly
D.Hash — an append-only log of entries with unique ids, supporting time-ordered reads, ranges, and consumer groups for messaging workloads
Answer + AI explanation with Pro
10. What is Sorted set?
Mid
A.a probabilistic structure that estimates the cardinality of a large set using roughly 12 KB regardless of element count, with about 0.81% standard error
B.the most basic Redis value type, a binary-safe sequence of bytes up to 512 MB holding text, numbers, or serialized objects
C.an ordered sequence of entries implemented as a linked structure where pushes and pops at either end run in constant time
D.a collection of unique members each ordered by an associated floating-point score, enabling fast range and rank queries
Answer + AI explanation with Pro
11. Which term means: "a collection of unique members each ordered by an associated floating-point score, enabling fast range and rank queries"?
Mid
A.Hash
B.Sorted set
C.String
D.HyperLogLog
Answer + AI explanation with Pro
12. Which statement is correct?
Mid
A.Sorted set — an append-only log of entries with unique ids, supporting time-ordered reads, ranges, and consumer groups for messaging workloads
B.Sorted set — a collection of unique members each ordered by an associated floating-point score, enabling fast range and rank queries
C.Sorted set — an extension of the string type letting you set, clear, and count individual bits by offset, perfect for compact boolean flags per id
D.Sorted set — a probabilistic structure that estimates the cardinality of a large set using roughly 12 KB regardless of element count, with about 0.81% standard error
Answer + AI explanation with Pro
13. What is Bitmap?
Mid
A.a probabilistic structure that estimates the cardinality of a large set using roughly 12 KB regardless of element count, with about 0.81% standard error
B.the most basic Redis value type, a binary-safe sequence of bytes up to 512 MB holding text, numbers, or serialized objects
C.an append-only log of entries with unique ids, supporting time-ordered reads, ranges, and consumer groups for messaging workloads
D.an extension of the string type letting you set, clear, and count individual bits by offset, perfect for compact boolean flags per id
Answer + AI explanation with Pro
14. Which term means: "an extension of the string type letting you set, clear, and count individual bits by offset, perfect for compact boolean flags per id"?
Mid
A.Hash
B.Bitmap
C.String
D.HyperLogLog
Answer + AI explanation with Pro
15. Which statement is correct?
Mid
A.Bitmap — an ordered sequence of entries implemented as a linked structure where pushes and pops at either end run in constant time
B.Bitmap — an extension of the string type letting you set, clear, and count individual bits by offset, perfect for compact boolean flags per id
C.Bitmap — a collection of unique members each ordered by an associated floating-point score, enabling fast range and rank queries
D.Bitmap — a value type mapping field names to values, ideal for representing a single object with many attributes compactly
Answer + AI explanation with Pro
16. What is HyperLogLog?
Senior
A.the most basic Redis value type, a binary-safe sequence of bytes up to 512 MB holding text, numbers, or serialized objects
B.a probabilistic structure that estimates the cardinality of a large set using roughly 12 KB regardless of element count, with about 0.81% standard error
C.an append-only log of entries with unique ids, supporting time-ordered reads, ranges, and consumer groups for messaging workloads
D.an ordered sequence of entries implemented as a linked structure where pushes and pops at either end run in constant time
Answer + AI explanation with Pro
17. Which term means: "a probabilistic structure that estimates the cardinality of a large set using roughly 12 KB regardless of element count, with about 0.81% standard error"?
Senior
A.String
B.HyperLogLog
C.Stream
D.Sorted set
Answer + AI explanation with Pro
18. Which statement is correct?
Senior
A.HyperLogLog — a collection of unique members each ordered by an associated floating-point score, enabling fast range and rank queries
B.HyperLogLog — a value type mapping field names to values, ideal for representing a single object with many attributes compactly
C.HyperLogLog — the most basic Redis value type, a binary-safe sequence of bytes up to 512 MB holding text, numbers, or serialized objects
D.HyperLogLog — a probabilistic structure that estimates the cardinality of a large set using roughly 12 KB regardless of element count, with about 0.81% standard error
Answer + AI explanation with Pro
19. What is Stream?
Senior
A.an extension of the string type letting you set, clear, and count individual bits by offset, perfect for compact boolean flags per id
B.an ordered sequence of entries implemented as a linked structure where pushes and pops at either end run in constant time
C.a probabilistic structure that estimates the cardinality of a large set using roughly 12 KB regardless of element count, with about 0.81% standard error
D.an append-only log of entries with unique ids, supporting time-ordered reads, ranges, and consumer groups for messaging workloads
Answer + AI explanation with Pro
20. Which term means: "an append-only log of entries with unique ids, supporting time-ordered reads, ranges, and consumer groups for messaging workloads"?
Senior
A.Hash
B.String
C.HyperLogLog
D.Stream
Answer + AI explanation with Pro
21. Which statement is correct?
Senior
A.Stream — a value type mapping field names to values, ideal for representing a single object with many attributes compactly
B.Stream — a probabilistic structure that estimates the cardinality of a large set using roughly 12 KB regardless of element count, with about 0.81% standard error
C.Stream — the most basic Redis value type, a binary-safe sequence of bytes up to 512 MB holding text, numbers, or serialized objects
D.Stream — an append-only log of entries with unique ids, supporting time-ordered reads, ranges, and consumer groups for messaging workloads
Answer + AI explanation with Pro
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