Quick Revision

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 → Operating System Basics 1

Kernel trick in SVM allows?
Non-linear classification by mapping data to higher-dimensional space
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Computer Fundamentals → Introduction to Computer 37

Random forest is an ensemble of?
Decision trees trained on random subsets with feature randomness
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Boosting ensemble method?
Trains models sequentially, each correcting previous model's errors
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XGBoost is based on?
Gradient boosted decision trees with regularization
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PCA (Principal Component Analysis) is used for?
Dimensionality reduction by finding principal variance directions
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t-SNE is used for?
High-dimensional data visualization in 2D/3D
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DBSCAN clustering algorithm?
Discovers clusters of arbitrary shape based on density
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Hierarchical clustering produces?
Dendrogram — tree showing cluster merges at different distances
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Autoencoder is used for?
Unsupervised feature learning, dimensionality reduction, anomaly detection
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GAN (Generative Adversarial Network) consists of?
Generator (creates fake data) and Discriminator (detects fakes) competing
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ACID vs BASE in databases: BASE means?
Basically Available, Soft-state, Eventually consistent
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CROSS JOIN produces?
Cartesian product — all combinations of rows from both tables
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SELF JOIN joins a table?
To itself
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Which SQL command changes table structure?
ALTER TABLE
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Database view vs materialized view: materialized view?
Stores result physically — faster queries but needs periodic refresh
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OLAP vs OLTP: OLAP is used for?
Analytical queries on large datasets (data warehousing)
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Star schema in data warehouse has?
Central fact table surrounded by dimension tables
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ETL stands for?
Extract, Transform, Load
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Which database is used for time-series data?
InfluxDB/TimescaleDB
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Graph databases like Neo4j use which query language?
Cypher
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Elasticsearch is primarily used for?
Full-text search and log analytics
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TF-IDF measures?
Term relevance — frequency in document vs rarity across documents
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Which is NOT a valid SQL aggregate function?
FIRST()
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RANK() vs DENSE_RANK() in SQL: difference is?
RANK() skips numbers after ties; DENSE_RANK() doesn't skip
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Window functions in SQL operate on?
Set of rows related to current row without collapsing them
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CTE (Common Table Expression) in SQL is defined using?
WITH clause — named temporary result set
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Recursive CTE is used for?
Hierarchical data queries (org charts, trees)
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Execution plan in SQL databases shows?
How the query will be executed (indexes used, join methods, cost)
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Serverless computing pricing model?
Pay only for actual execution time and resources consumed
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AWS Lambda maximum execution timeout is?
15 minutes
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Cold start in serverless refers to?
Latency when a new container/instance initializes for first invocation
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Event-driven architecture responds to?
Events/triggers automatically — loose coupling between services
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Message queue vs event stream: event stream?
Retains events for replay by multiple consumers (Kafka)
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Dead Letter Queue (DLQ) stores?
Messages that failed to process after maximum retry attempts
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Content Delivery Network (CDN) edge nodes are placed?
Geographically distributed close to end users
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CDN reduces load on origin server by?
Serving cached content from edge nodes instead of origin
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Cache invalidation in CDN is triggered by?
Content publisher via API/TTL expiry
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Which AWS service is an object storage?
S3
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Computer Fundamentals → Memory Units 1

Which SQL join returns all from left table even with no right match?
LEFT JOIN
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Computer Fundamentals → Internet Basics 1

Inverted index is used by search engines to?
Map words to documents containing them (enables fast text search)
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