Ch10 ElastiCache

Question 1

Which of the following objects are good candidates to store in a cache? (Choose 3
answers)
A. Session state
B. Shopping cart
C. Product catalog
D. Bank account balance

Answer 1

A, B, C. Many types of objects are good candidates to cache because they have the
potential to be accessed by numerous users repeatedly. Even the balance of a bank
account could be cached for short periods of time if the back-end database query is slow
to respond.

Question 2

Which of the following cache engines are supported by Amazon ElastiCache? (Choose 2
answers)
A. MySQL
B. Memcached
C. Redis
D. Couchbase

Answer 2

B, C. Amazon ElastiCache supports Memcached and Redis cache engines. MySQL is not a
cache engine, and Couchbase is not supported.

Question 3

How many nodes can you add to an Amazon ElastiCache cluster running Memcached?
A. 1
B. 5
C. 20
D. 100

Answer 3

C. The default limit is 20 nodes per cluster.

Question 4

How many nodes can you add to an Amazon ElastiCache cluster running Redis?
A. 1
B. 5
C. 20
D. 100

Answer 4

A. Redis clusters can only contain a single node; however, you can group multiple
clusters together into a replication group.

Question 5

An application currently uses Memcached to cache frequently used database queries.
Which steps are required to migrate the application to use Amazon ElastiCache with
minimal changes? (Choose 2 answers)
A. Recompile the application to use the Amazon ElastiCache libraries.
B. Update the configuration file with the endpoint for the Amazon ElastiCache cluster.
C. Configure a security group to allow access from the application servers.
D. Connect to the Amazon ElastiCache nodes using Secure Shell (SSH) and install the
latest version of Memcached.

Answer 5

B, C. Amazon ElastiCache is Application Programming Interface (API)-compatible with
existing Memcached clients and does not require the application to be recompiled or
linked against the libraries. Amazon ElastiCache manages the deployment of the Amazon
ElastiCache binaries

Question 6

How can you back up data stored in Amazon ElastiCache running Redis? (Choose 2
answers)
A. Create an image of the Amazon Elastic Compute Cloud (Amazon EC2) instance.
B. Configure automatic snapshots to back up the cache environment every night.
C. Create a snapshot manually.
D. Redis clusters cannot be backed up.

Answer 6

B, C. Amazon ElastiCache with the Redis engine allows for both manual and automatic
snapshots. Memcached does not have a backup function.

Question 7

How can you secure an Amazon ElastiCache cluster? (Choose 3 answers)
A. Change the Memcached root password.
B. Restrict Application Programming Interface (API) actions using AWS Identity and
Access Management (IAM) policies.
C. Restrict network access using security groups.
D. Restrict network access using a network Access Control List (ACL).

Answer 7

B, C, D. Limit access at the network level using security groups or network ACLs, and
limit infrastructure changes using IAM.

Question 8

You are working on a mobile gaming application and are building the leaderboard feature
to track the top scores across millions of users. Which AWS services are best suited for
this use case?
A. Amazon Redshift
B. Amazon ElastiCache using Memcached
C. Amazon ElastiCache using Redis
D. Amazon Simple Storage Service (S3)

Answer 8

C. Amazon ElastiCache with Redis provides native functions that simplify the
development of leaderboards. With Memcached, it is more difficult to sort and rank large
datasets. Amazon Redshift and Amazon S3 are not designed for high volumes of small
reads and writes, typical of a mobile game.

Question 9

You have built a large web application that uses Amazon ElastiCache using Memcached
to store frequent query results. You plan to expand both the web fleet and the cache fleet
multiple times over the next year to accommodate increased user traffic. How do you
minimize the amount of changes required when a scaling event occurs?
A. Configure AutoDiscovery on the client side
B. Configure AutoDiscovery on the server side
C. Update the configuration file each time a new cluster
D. Use an Elastic Load Balancer to proxy the requests

Answer 9

A. When the clients are configured to use AutoDiscovery, they can discover new cache
nodes as they are added or removed. AutoDiscovery must be configured on each client
and is not active server side. Updating the configuration file each time will be very
difficult to manage. Using an Elastic Load Balancer is not recommended for this
scenario.

Question 10

Which cache engines does Amazon ElastiCache support? (Choose 2 answers)
A. Memcached
B. Redis
C. Membase
D. Couchbase

Answer 10

A, B. Amazon ElastiCache supports both Memcached and Redis. You can run self-
managed installations of Membase and Couchbase using Amazon Elastic Compute Cloud
(Amazon EC2).