A reporting database on RDS for MySQL shows rising read latency while CPU stays near 20 percent. Freeable memory keeps falling and read IOPS climb whenever the large reports run. What is the most likely cause and the best fix?
Show answer and explanation
Answer: A
Low CPU alongside rising read latency and I/O, with freeable memory falling, points to memory pressure. When frequently accessed data exceeds the buffer pool, pages must be fetched from storage, which slows reads. A larger memory class gives the cache room, and moving reporting reads to a read replica keeps that work from competing with the primary's cache and I/O.
Why the other options are wrong
- B. With CPU near 20 percent, the processors are not the constraint, so adding vCPUs would leave the latency pattern and the falling memory unchanged.
- C. Network or security group problems usually produce connection timeouts and errors across many metrics, not a steady rise in read I/O while available memory shrinks.
- D. Corruption is rare on managed RDS storage and would not produce a gradual memory decline with more read I/O, so restoring a snapshot would not address the underlying cause.