ElastiCache Strategies

Two Caching Implementation Strategies

• Lazy Loading / Cache-Aside / Lazy Population

• WriteThrough

Lazy-Loading

Pros:

• Only requested data is cached; no useless data

• Node failures are not fatal (just increased latency to warm cache)

Cons:

• Cache miss penalty will result in 3 round trips, noticeable delay in initial request

• Stale data: data can be updated in database and outdated in the cache

WriteThrough

Pros:

• Data in dcache is never stale, reads are quick

• Write penalty instead of ready penalty (each write requires 2 calls)

Cons:

• Missing Data until it is added/updated in the DB. Mitigation is to implement Lazy-Loading strategy in conjunction

• Cache churn - a lot of the data will never be read into the cache

Managing Cache with Cache Evictions and Time-To-Live (TTL)

Eviction can occur in three ways:

1. Delete item explicitly in the cache

2. Item evicted due to full memory and not been recently used (LRU)

3. Set item time-to-live (TTL)

TTL can range from a few seconds to hours and days.