Application cache at the data-center

Question 1

Potential problems of database and solution

Answer 1

• Slow… databases store data on disk.
• Cost… cloud platforms pay-per-use model: each access is
  charged.

Cache layer

Question 2

Problems with cache data in the application server machine

Answer 2

The size of the cache is limited to the memory of each
machine.
Distributing the load means that the same data will be
cached in multiple machines.

Question 3

Advantages in sharing cache among multiple machines

Answer 3

Advantages:
* Much larger cache size than caching only in the local memory.
* Pricing: cache access is cheaper than the database access at scale.

Question 4

Advantages in sharing cache among multiple machines

Answer 4

Disadvantages:
* Slower when compared to access to the local memory.

Question 5

Common uses of caches

Answer 5

• Content Caching
  Store data that changes infrequently – e.g. page templates, data
  modified periodically (e.g. main page in a newspaper), etc.
  Reduces the processing time and server load.
• Cache-Aside
  Cache part of the database for faster access. Modify the cache when
  modifying the backend data.
  Reduces the server load.
• User session caching
  Store information associated with a user session in cache instead of (or
  in addition to) on the database. E.g. store info such as history,
  shopping carts, etc.
  Allows faster interaction; Client requests can be processed by any
  server.