201. What is a time-series database optimized for?
- a) Storing and querying timestamped data points
- b) Managing temporal tables
- c) Storing historical backups
- d) Tracking transaction times
Answer: A - Time-series databases (e.g., InfluxDB, TimescaleDB) excel at metrics, events, and IoT data with time-based queries.
202. What is the purpose of a database write-through cache?
- a) To update cache and storage simultaneously on writes
- b) To cache only write operations
- c) To delay writes to storage
- d) To compress write buffers
Answer: A - Write-through ensures cache and database remain consistent but has higher write latency.
203. Which of the following is NOT a time-series database compression technique?
- a) Delta encoding
- b) Gorilla compression
- c) Dictionary encoding
- d) Bubble compression
Answer: D - Time-series DBs use delta encoding (for timestamps), Gorilla (for floats), and dictionary (for strings).
204. What is database governance?
- a) Policies and processes for data quality, security, and compliance
- b) Government database regulations
- c) A type of distributed database
- d) Database backup management
Answer: A - Governance includes data lineage, access controls, and audit trails to meet regulatory requirements.
205. What is the purpose of a time-series database retention policy?
- a) To automatically expire old data based on time rules
- b) To manage database licenses
- c) To control memory usage
- d) To limit user access duration
Answer: A - Retention policies (e.g., "keep 30 days of raw data") manage storage costs for high-volume time-series data.
206. What is polyglot persistence?
- a) Using different database technologies for different data needs
- b) A multilingual database schema
- c) A type of durable storage
- d) A backup rotation strategy
Answer: A - Polyglot persistence combines relational, document, graph, etc. databases in one system.
207. What is the purpose of a database write-around cache?
- a) To bypass cache for writes while still caching reads
- b) To write to cache in a circular buffer
- c) To distribute writes across multiple caches
- d) To compress write operations
Answer: A - Write-around avoids cache pollution for write-heavy workloads but may cause read misses.
208. What is a time-series database downsampling?
- a) Reducing data resolution over time to save space
- b) Sampling database queries
- c) Distributing time-series data across servers
- d) A compression failure mode
Answer: A - Downsampling aggregates raw data into lower-resolution summaries (e.g., keep 1-minute samples after 7 days).
209. What is database reliability engineering (DRE)?
- a) Applying SRE principles to database systems
- b) A type of database backup
- c) Hardware redundancy for databases
- d) A certification program
Answer: A - DRE focuses on availability, performance, and change management through automation and monitoring.
210. What is the purpose of the SQL TIME_BUCKET function?
- a) To group time-series data into fixed intervals
- b) To allocate time resources
- c) To schedule database jobs
- d) To measure query execution time
Answer: A - TIME_BUCKET (in TimescaleDB) enables efficient time-based aggregations like "per 5-minute bucket".
211. What is cache stampede in database systems?
- a) Concurrent requests triggering multiple cache regenerations
- b) A type of cache corruption
- c) Rapid cache eviction
- d) A security attack on caches
Answer: A - Stampedes occur when expired cache items trigger thundering herds of duplicate computations.
212. What is the purpose of a time-series database continuous aggregate?
- a) To maintain pre-computed aggregations that refresh automatically
- b> To implement real-time analytics
- c> To combine multiple time-series
- d> A type of materialized view
Answer: A - Continuous aggregates (e.g., in TimescaleDB) efficiently maintain rolling summaries like daily averages.
213. What is database chaos engineering?
- a) Intentionally injecting failures to test resilience
- b> A disorganized database design
- c> A type of NoSQL database
- d> An optimization technique
Answer: A - Chaos experiments (e.g., killing nodes, adding latency) reveal weaknesses in distributed databases.
214. What is the purpose of the SQL LAST_VALUE function in time-series queries?
- a> To get the most recent value in a time-ordered window
- b> To find the last inserted record
- c> To return historical values
- d> To implement FIFO queues
Answer: A - LAST_VALUE() with ORDER BY time DESC helps find current states in time-series data.
215. What is write-behind caching?
- a> Acknowledging writes to cache before persisting to database
- b> Writing to cache in background threads
- c> A type of cache invalidation
- d> Delayed write operations
Answer: A - Write-behind improves write latency but risks data loss if cache fails before database update.
216. What is the purpose of the SQL TIME_SERIES_JOIN operation?
- a> To align time-series data with different timestamps
- b> To combine time tables
- c> To join temporal databases
- d> To schedule queries
Answer: A - Time-series joins interpolate values to align measurements (e.g., CPU and memory at same moments).
217. What is a database circuit breaker pattern?
- a> Failing fast when dependent services are unavailable
- b> An electrical safety feature
- c> A query cancellation mechanism
- d> A type of replication
Answer: A - Circuit breakers prevent cascading failures by rejecting requests during outages.
218. What is the purpose of the SQL TIME_WINDOW function?
- a> To define sliding or tumbling windows for time-series analysis
- b> To schedule maintenance windows
- c> To limit query execution time
- d> To partition time-series data
Answer: A - TIME_WINDOW enables operations like "5-minute moving averages" in time-series databases.
219. What is database cache warming?
- a> Preloading frequently accessed data into cache
- b> Increasing cache temperature for performance
- c> A type of cache compression
- d> A security technique
Answer: A - Cache warming reduces cold-start latency after deployments or restarts.
220. What is the purpose of the SQL RATE function in time-series databases?
- a> To calculate per-second change metrics
- b> To compute interest rates
- c> To measure query throughput
- d> To rank time-series data
Answer: A - RATE() converts counter increments (e.g., network bytes) into per-second values, handling resets.