1. Increase performance, increase scalability, decrease database or backend burden, decrease costs.
2. Memcached and Redis.
3. Memcached supports only simple datasets.
4. Implement Memcached caching and move the session state into the cache cluster.
5. Use Memcached to store the write-through data. Point your SQL application straight to the database, as no cache engine supports SQL.

6. Increasing the number of nodes can only be done by adding read replicas, so this isn't possible.
7. Decrease the TTL for your cache accordingly, as stale data is being kept in the cache and delivered to the BI nightly report.