aws elasticache in memory storage for rds
Memory is faster than disk. Elasticache is a way to speed database queries by storing frequently accessed data in an in-memory cache.
- In-memory cache (key value) - easy to deploy, operate, and scale in-memory cache in the cloud
- Improves DB performance - retrieving information in faster caches than disk-based storage
- Good for read-heavy DB workloads (caching results of I/O intensive queries)
- Useful for session data on distributed applications
An Elasticache cluster can store the frequently accessed data, then the application would query the cache instead of the database.
Memcached
Great for basic object caching, scaling horizontally, with no persistence.
This has no multi AZ or failover options. However, it is a good choice if you want basic caching and it to be as simple as possible.
Redis
A more sophisticated solution with enterprise features like persistence, replication, multi AZ, failover.
This also supports sorting and ranking data (like gaming leaderboards), lists, and other complex data types.
Typical exam scenario
- Database under stress
- Find a solution
- What service would alleviate this
- Know when to use Elasticache
- This is a good if your database is read-heavy and not prone to frequent changes
When not to use elasticache
- Heavy write loads
- Caching doesn't alleviate heavy writes, you'd need to scale up the DB instead
- OLAP queries with analytical loads
- This is basically any complex, long running query. Use RedShift instead.