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GK One-Line Question & Answer

15541+ short questions with short answers, covering every category and sub-category on the site — no long articles to scroll through. Good for a fast recap before an exam, or a few minutes of daily practice.

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Computer Fundamentals → Introduction to Computer 39

Which scheduling policy is used for real-time tasks in Linux?
SCHED_FIFO or SCHED_RR
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I/O scheduler in Linux determines?
Order and priority of I/O requests to storage devices
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Which I/O scheduler is best for SSDs?
None/mq-deadline
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Futex (Fast Userspace muTEX) in Linux?
Operates mostly in userspace — falls to kernel only on contention
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Lock-free data structures use?
Atomic operations to ensure thread safety without locks
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ABA problem in lock-free programming occurs when?
Value changes A→B→A appearing unchanged to CAS, causing incorrect operation
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B+ tree advantages over B-tree for database indexing?
All data in leaf nodes + linked leaves enable efficient range queries
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LSM tree (Log-Structured Merge tree) is used in?
Write-optimized databases like LevelDB, RocksDB, Cassandra
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Skip list provides?
O(log n) average search with probabilistic balance (simpler than balanced BST)
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Consistent hashing is used in?
Distributed systems for even load distribution as nodes join/leave
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CAP theorem states a distributed system can guarantee only two of?
Consistency, Availability, Partition tolerance
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In CAP theorem, CP system prioritizes?
Consistency and Partition tolerance — may be unavailable during partition
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AP system in CAP theorem?
Prioritizes Availability and Partition tolerance — may return stale data
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PACELC theorem extends CAP by also considering?
Latency vs Consistency tradeoff when no partition exists
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MapReduce programming model consists of?
Map phase (parallel processing) + Reduce phase (aggregation)
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Apache Hadoop uses MapReduce on?
HDFS distributed file system across cluster
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Apache Spark is faster than MapReduce because?
In-memory processing instead of disk I/O between stages
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Directed Acyclic Graph (DAG) in Spark represents?
Task execution plan with dependencies
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Stream processing vs batch processing: stream processes?
Data in real time as it arrives
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Apache Kafka is a?
Distributed event streaming platform (message queue)
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Kafka topic partition allows?
Parallel consumption and horizontal scaling
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Event sourcing pattern stores?
All state changes as immutable sequence of events
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CQRS (Command Query Responsibility Segregation) separates?
Read (query) and write (command) data models
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Saga pattern in microservices handles?
Distributed transactions through sequence of local transactions with compensations
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Circuit breaker pattern in microservices?
Prevents cascading failures by stopping requests to failing service
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Service discovery in microservices allows?
Dynamic detection of service instances and their locations
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Which algorithm detects cycles in a directed graph?
DFS with coloring (White-Gray-Black)
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Articulation point in a graph is?
Vertex whose removal disconnects the graph
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Tarjan's algorithm finds?
Strongly Connected Components (SCCs) in directed graph
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Kosaraju's algorithm for SCCs performs how many DFS passes?
2
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Maximum flow problem solution includes?
Ford-Fulkerson / Edmonds-Karp algorithm
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Fenwick tree (Binary Indexed Tree) is used for?
Efficient prefix sum queries and point updates in O(log n)
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Segment tree supports?
Range queries and range updates in O(log n)
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Sparse table is used for?
Static range minimum/maximum queries in O(1) after O(n log n) preprocessing
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Disjoint Set Union (DSU/Union-Find) with path compression and union by rank achieves?
Near O(1) amortized per operation (inverse Ackermann function)
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Knuth-Morris-Pratt (KMP) string matching algorithm runs in?
O(n+m) using failure function
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Gradient descent optimization minimizes?
Loss function by iteratively adjusting weights
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Mini-batch gradient descent uses?
Small random subset of samples per update
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Adam optimizer combines?
RMSprop and Momentum — adaptive learning rates per parameter
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Computer Fundamentals → Memory Units 1

Stochastic Gradient Descent (SGD) differs from batch GD in?
Updates weights using single random sample per iteration
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