Q15 (20 points) Choose the description that is incorrect regarding the differences between...
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(20 points)
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 RAM, which is volatile memory. When power is lost or the system fails, data in RAM is lost immediately unless explicitly persisted to disk. In contrast, traditional databases like MySQL and PostgreSQL store data on persistent storage (HDD/SSD), making them more resilient to physical failures. Therefore, in-memory databases are actually more susceptible to data loss from hardware failures, not less.
Step-by-step Derivation:
Evaluate each statement:
A) CORRECT – In-memory databases (Redis, Memcached) access data from RAM, which has nanosecond latencies, vs. disk I/O (milliseconds) in MySQL/PostgreSQL. Speed advantage is well-established.
B) INCORRECT – RAM is volatile. Power loss = complete data loss. Traditional databases persist to stable storage (HDD/SSD), surviving hardware failures. In-memory DBs are more vulnerable, not resilient.
C) CORRECT – In-memory databases rely primarily on having enough RAM. They use eviction policies (LRU, etc.) as a secondary capacity strategy, but the primary design assumes sufficient main memory availability.
D) CORRECT – Redis and Memcached are textbook examples of in-memory key-value stores.
Answer: B is the incorrect statement.