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Flashcards

DynamoDB

Sam Wells AWS Associate Developer Inglês 55 flashcards

Flashcards do conjunto (55)

  1. 1What type of storage is a DynamoDb instance stored on?SSD Storage
  2. 2DynamoDB is an example of a NoSQL DBTrue
  3. 3How many different consistency models are there for DynamoDB?2
  4. 4What are the different Consistency Models for DynamoDb?Eventual Consistency
    Strongly Consistent Reads
  5. 5What is the default consistency model for DynamoDb?Eventual Consistency
  6. 6What is the Eventually Consistency model?Consistency across all data copies usually reached within 1 second, i.e. If you update a value, that value should be updated when read after 1 second
  7. 7What is the Strongly Consistent Read model?Read returns a result reflecting all writes that received a successful response prior to the read
  8. 8A DynamoDB table consists of...Items (Table Row)
    Attributes (Table Column)
  9. 9What are the different types of Primary Key?Partition Key
    Composite Key
  10. 10What is a Partition Key?Unique attribute, e.g. User ID
  11. 11How is a Partition Key stored?Value of partition key input into hash function which determines partition (physical location) at which the data is stored
  12. 12What is a Composite Key?Partition Key + Sort Key in combination
  13. 13What is an example of a Composite Key?User Forum Example
    Primary Key = User ID
    Sort Key = Timestamp of post
  14. 142 items can have the same Partition Key, but must have a different Sort KeyTrue
  15. 15What condition, when added to an IAM policy enables a user to view/manipulate their data when the Partition Key matches their user ID?LeadingKeys Parameter
  16. 16What is an SQL DB index?A data structure that allows you to perform fast queries on specific columns in a table, rather than the entire dataset.
  17. 17What is a DynamoDB Index?Enable fast queries on specific data columns and provide a different view of you data based on an alternative Partition/Sort Keys
  18. 18What are the 2 different types of indexes?Local Secondary Index
    Global Secondary Index
  19. 19What is a Local Secondary Index?- Can only be created when creating your table
    - Cannot add/remove/modify later
    - Has same partition key as the original table, but a different sort key
    - Any queries based on sort key are much faster than using the main table
  20. 20What is a Global Secondary Index?- Can be created on table creation or can be added later
    - Can use a different partition key as well as a different sort key
  21. 21What is a Scan?- Examines every item in the table
    - Returns all attributes by default
  22. 22What parameter can be used to refine the results of a Scan/Query?ProjectionExpression parameter
  23. 23What is a Query?- Find items in table based on Primary Key and a distinct value to search for
    - You can use on optional sort key name and value to refine the results - e.g. if sort key is timestamp, you can refined to only select items from last 7 days
    - All attributes returned by default
  24. 24Queries are not Eventually Consistent by defaultFalse - They are eventually consistent by default
  25. 25Queries vs. Scans- Query more efficient
    - As table grows, scan operations take longer
  26. 26How can you improve the performance of a Scan query?- Use smaller page size, using fewer read options
    - Isolate to specific tables
    - Use parallel scans rather than sequential
    - Design tables to avoid using Scans
  27. 27What is Provisioned Throughput measured in?Capacity Units
  28. 281 Write Capacity Unit is equal to...1 x 1KB Write per second
  29. 291 Strongly Consistent Read Capacity Unit is equal to...1 x 4KB per second
  30. 301 Eventually Consistent Read Capacity Unit is equal to...2 x 4KB per second
  31. 31How do you calculate how many Read Capacity units are required for a Strongly Consistent read?1. Divide size of each item by 4KB
    2. Round result up to nearest whole number
    3. Multiply by the number of reads per second
  32. 32Read Capacity - Strongly Consistent Example 80 Items (Table Rows) per second, each item 3Kb in size3KB / 4KB = 0.75
    0.75 = 1
    1 x 80 = 80
  33. 33How do you calculate how many Read Capacity units are required for a Eventually Consistent read?1. Divide size of each item by 4KB
    2. Round result up to nearest whole number
    3. Multiply by the number of reads per second
    4. Divide this number by 2
  34. 34Read Capacity - Eventually Consistent Example 80 Items (Table Rows) per second, each item 3Kb in size3KB / 4KB = 0.75
    0.75 = 1
    1 x 80 = 80
    80 / 2 = 40
  35. 35How do you Calculate Write capacity?1. Divide size of each item by 1KB
    2. Round up to nearest whole number
    3. Multiply by number of writes per second
  36. 36Write Capacity example Write 100 items per second, each item is 512 bytes in size512 bytes / 1kb = 0.5
    0.5 = 1
    1 * 100 = 100
  37. 37What is Dynamo Accelerator (DAX)?Fully managed, clustered in-memory cache for DynamoDB
  38. 38What performance improvement does DAX offer?10X read performance improvement
    EVENTUALLY CONSISTENT READS ONLY
  39. 39DAX offers a Write-through caching service, what is this?Data is written to the cache as well as the back end store at the same time
  40. 40What is a cache hit?When the requested data is found and returned from the cache
  41. 41What is a cache miss?When the requested data is not found in the cache
  42. 42What does DAX do in the event of a cache miss?Performs an eventually consistent read on the DynamoDb table
  43. 43What is DAX not suitable for?- Strongly consistent reads
    - Write intensive applications
    - Applications that don't read often
    - Applications that don't require microsecond response times
  44. 44What is Elasticache?In memory caching that sits between application and DB
  45. 45How is Elasticache different to DAX?DAX is specifically for DynamoDB whereas Elasticache is utilised for other DB types
  46. 46What are the 2 different types of Elasticache?Memcached
    Redis
  47. 47What are the main characteristics of Memcache?+ Widely Adopted
    + Multi-threaded
    - No multi-AZ
  48. 48What are the main characteristics of Redis?+ Open source key-value store
    + Supports more complex data structures
    + Supports Master/Slave replication and Multi-AZ for cross AZ redundancy
  49. 49What are the Elasticache strategies?Lazy Loading
    Write Through
  50. 50What is the Lazy Loading caching strategy?- Loads data into cache only when necessary
    - If requested data in cache it is returned, otherwise NULL, then retrieves data for next time
    - TTL on data to avoid keeping stale data
  51. 51What is the Write Through caching strategy?- Adds/Updates cache data whenever database is written to
    - Prevents stale data in cache
    - Can result in wasted resources if most data not read
  52. 52What is DynamoDB TTL?TTL - Time to Live
    A time set that once expired, marks data for deletion which is then deleted in 48hrs
  53. 53What are DynamoDB streams?Time ordered sequence of modifications made to your table
  54. 54DynamoDB streams are encryptedTRUE
  55. 55How long are DynamoDB streams retained for?24 Hrs

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Associate Developer AWS FlashCards sobre DynamoDB, criado por Sam Wells em 26-04-2019.
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Sam Wells
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