What is the correct indicator that the cache size should be increased?

What is the correct indicator that the cache size should be increased?

• A. Low usage percentage
• B. High CPU usage
• C. High usage percentage above 75%
• D. High memory usage

Answer: (C)

When deciding to grow a cache, the key signal is how full the cache is and how often items have to be evicted. A cache that’s almost full means it’s starting to hold the same data as before more often, and evictions become frequent, which can lead to more cache misses and slower performance because data has to be fetched from the slower backend. If usage stays high, especially above a practical threshold like 75%, it indicates the cache is near capacity and may no longer be efficiently serving requests. Increasing the cache size in this situation helps keep more of the hot data in memory, reducing misses and improving response times. Low usage means there’s plenty of free space, so there’s no pressing need to expand. High CPU usage isn’t a direct indicator of cache capacity problems—it could be due to many other factors. High memory usage could signal overall memory pressure, but it doesn’t specifically tell you that the cache itself needs to grow.

When deciding to grow a cache, the key signal is how full the cache is and how often items have to be evicted. A cache that’s almost full means it’s starting to hold the same data as before more often, and evictions become frequent, which can lead to more cache misses and slower performance because data has to be fetched from the slower backend.

If usage stays high, especially above a practical threshold like 75%, it indicates the cache is near capacity and may no longer be efficiently serving requests. Increasing the cache size in this situation helps keep more of the hot data in memory, reducing misses and improving response times.

Low usage means there’s plenty of free space, so there’s no pressing need to expand. High CPU usage isn’t a direct indicator of cache capacity problems—it could be due to many other factors. High memory usage could signal overall memory pressure, but it doesn’t specifically tell you that the cache itself needs to grow.