Practice Test

True/False: In AWS, the Amazon ElastiCache service is used for caching.

  • True
  • False

Answer: True

Explanation: Amazon ElastiCache is a fully managed caching service provided by AWS. It improves the performance of web applications by allowing you to retrieve information from fast, managed, in-memory caches, instead of relying entirely on slower disk-based databases.

Multiple Select: Which of the following are popular caching strategies?

  • A. Write-through cache
  • B. Read-through cache
  • C. Write-back cache
  • D. Short-up cache

Answer: A, B, C

Explanation: Write-through cache, Read-through cache, and Write-back cache are popular caching strategies used to improve performance. Short-up cache is not a recognized caching strategy.

True/False: TTL (Time To Live) is not a valid cache eviction policy in AWS.

  • True
  • False

Answer: False

Explanation: TTL, or time-to-live, is a concept used in caching that determines the lifespan of data in a cache. AWS ElastiCache does support TTL as a cache eviction policy.

Single Select: In which database caching strategy does every write operation go to cache first and then to the database?

  • A. Write-through cache
  • B. Read-through cache
  • C. Write-around cache
  • D. Write-back cache

Answer: A. Write-through cache

Explanation: In a write-through cache, every write operation goes to the cache first and then to the database. It ensures no loss of data even if the system fails or reboots.

Multiple Select: When you design a caching system, which of the following are important to consider?

  • A. Cache size
  • B. Cache eviction policy
  • C. Cache inclusion policy
  • D. All of the above

Answer: D. All of the above

Explanation: It’s important to correctly size the cache, pick the right eviction policy, and decide on an inclusion policy that best fits the needs of your application.

True/False: Read-through caching strategy serves read requests directly from the database.

  • True
  • False

Answer: False

Explanation: Read-through caching strategy serves read requests from the cache. If the requested data is not in the cache, it pulls it from the database and stores it in the cache.

Single Select: In AWS, ElastiCache supports which types of data stores?

  • A. MongoDB
  • B. Cassandra
  • C. Redis and Memcached
  • D. MySQL

Answer: C. Redis and Memcached

Explanation: ElastiCache in AWS natively supports two open-source in-memory data stores: Redis and Memcached.

True/False: In write-back caching strategy, the data is written to cache and database simultaneously.

  • True
  • False

Answer: False

Explanation: In write-back caching, data is written to cache first and the write to the database happens later, not simultaneously.

Multiple Select: Which of the following eviction policies are supported by Elasticache for Redis?

  • A. volatile-lru
  • B. allkeys-lru
  • C. no-eviction
  • D. All of the above

Answer: D. All of the above

Explanation: AWS ElastiCache for Redis supports a number of different eviction policies, including volatile-lru, allkeys-lru, and no-eviction.

True/False: You can’t define your own caching policies in AWS ElastiCache.

  • True
  • False

Answer: False

Explanation: While AWS ElastiCache provides several built-in caching policies, you can also define your own caching policies to best meet your application’s needs.

Interview Questions

What is caching in the context of AWS?

Caching in AWS involves storing copies of data in a fast access layer (cache), allowing high-performance, scalable delivery to users.

What are the important factors to consider when selecting a caching strategy?

Important factors include the cache’s location, the volume of read and write operations, the cost, and the consistency of the application’s dataset.

What type of caching strategy does Amazon ElastiCache use?

Amazon ElastiCache provides in-memory caching and supports two open-source in-memory caching engines: Memcached and Redis.

When is write-through caching strategy useful?

Write-through caching is useful when there are more write operations than read operations, as it maintains consistency between the cache and the storage.

What is the definition of a cache hit?

A cache hit is when the data queried by an application is found in the cache.

What is the role of TTL (Time to Live) in caching strategies?

TTL is a mechanism that determines how long data should be stored in the cache before it is automatically removed. This helps manage the efficiency and freshness of the data in the cache.

What is lazy loading in caching strategy?

Lazy loading refers to the process of loading data into cache only when it is required by the application. It helps in reducing cache memory usage.

How does the Amazon CloudFront service tie into caching strategies?

Amazon CloudFront is a content delivery network that uses edge locations to cache and deliver content closer to the end user for faster delivery.

How does Amazon S3 support caching?

Amazon S3 supports caching through the use of metadata headers. This allows static assets to be cached at the browser level and at the CloudFront edge locations.

Can Amazon RDS instances be used as a caching layer?

Amazon RDS instances are generally not used as caching layers due to their persistent nature. Instead, AWS services like ElastiCache or DynamoDB DAX are more suitable for this role.

What is the purpose of the Amazon ElastiCache for Redis backup and restore feature?

This feature allows you to create data backups, and to restore your data for disaster recovery, analysis or cross-region replication.

What is the purpose of cache eviction policies in AWS ElastiCache?

Cache eviction policies decide which items to remove from the cache when the cache is full.

What is the write-around caching strategy?

In write-around caching, data is written directly to permanent storage, bypassing the cache. This can be useful if certain data isn’t likely to be re-read in the near future.

How is data consistency achieved in caching strategy?

Data consistency is achieved through different strategies like write-through, write-around, or write-back all of which handle how data is written to the cache and the backing store.

Why might a cache miss occur?

A cache miss occurs when the data an application requests is not found in the cache and has to be fetched from the origin server. This can occur if the data hasn’t been requested recently, and hence not stored in the cache or if the cache doesn’t have enough space to hold the data.

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