Caching Strategies

Preview — 3 of 10 questions

Which description best matches the cache-aside (lazy loading) pattern?

javascript

1. App checks cache → HIT  → return cached value (fast path)
2. App checks cache → MISS → query DB
3. App stores result in cache with TTL
4. App returns result to caller

AThe cache automatically pulls data from the database when a key is missing.

BThe application checks the cache first; on a miss, it fetches from the database, stores the result in cache, then returns it.

CEvery write to the database immediately updates the cache in the same transaction.

DThe cache is pre-populated with all data at startup before any request arrives.

What is the key difference between write-through and write-behind (write-back) caching?

javascript

Write-through:
  App → Cache → DB (synchronous, same request)
  Latency: higher (waits for DB write)
  Durability: strong (data always in DB)

Write-behind (write-back):
  App → Cache → ACK returned immediately
              → DB (async, seconds or minutes later)
  Latency: lower
  Durability risk: data in cache only until flush

AWrite-through updates cache and database synchronously on every write; write-behind updates the database asynchronously after acknowledging the write to the cache.

BWrite-through updates the cache only; write-behind updates both cache and database.

CWrite-through is faster because it skips the database entirely.

DWrite-behind is used exclusively for read-heavy workloads.

A cache is full and must evict an entry to make room. Which eviction policy removes the entry that has not been used for the longest time?

ALFU (Least Frequently Used)

BFIFO (First In, First Out)

CLRU (Least Recently Used)

DMRU (Most Recently Used)

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