Choose the description that is incorrect regarding the differences between in-memory...
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Choose the description that is incorrect regarding the differences between in-memory databases and traditional databases like MySQL or PostgreSQL.
Show answer & explanation
Option B is incorrect because in-memory databases store data in volatile RAM, which loses all contents on power failure or system crash—the opposite of being resilient to hardware failure. Storage-based databases like MySQL persist data to disk, making them more resilient to data loss. Options A, C, and D are all correct: in-memory databases are faster, typically use eviction policies (like LRU) when memory fills up, and Redis/Memcached are standard examples.
Step-by-step Derivation:
Evaluate each statement:
A) TRUE — In-memory databases access data from RAM (100 ns latency) rather than disk (10 ms latency), making them orders of magnitude faster.
B) FALSE — In-memory databases store data in volatile RAM. On hardware failure, power loss, or crash, all data is lost immediately. Traditional disk-based databases persist data to non-volatile storage (HDD/SSD), surviving such failures. In-memory databases are MORE vulnerable, not less.
C) TRUE — When in-memory databases approach capacity limits, they use eviction policies (LRU, LFU, TTL) to automatically delete infrequently used data rather than simply requiring more RAM. This is a key feature of systems like Redis and Memcached.
D) TRUE — Redis and Memcached are the canonical examples of in-memory key-value stores.
The question asks for the incorrect statement. Only B is incorrect.