DynamoDB

Question 1

DynamoDB

Write Capacity Unit

Answer 1

• one write per second for an item up to 1 KB in size
• (ITEM SIZE (rounded up to the next 1KB)/1KB) * # of items

Example: we write 10 objects per second of 2KB each.
- we need 2 * 10 = 20 WCU

Question 2

DynamoDB

Read Capacity Unit

Answer 2

• 4 KB units
• 1 strongly consistent read request
• 2 eventually consistent read request
• (ITEM SIZE (rounded up to the next 4KB)/4KB) * # of items.

Question 3

DynamoDB Streams

Answer 3

• ordered flow of information about changes to the items in the table
• all data in the stream is subject to a 24 hour life time.

Question 4

DynamoDB Stream View Types

Answer 4

KEYS_ONLY
NEW_IMAGE
OLD_IMAGE
NEW_AND_OLD_IMAGE

Question 5

DynamoDB

Global Secondary Index

Answer 5

• speed up queries on non-key attributes
• contains selection of attributes from the base table but are organized by a primary key
• queries support eventual consistency attributes
• basically creates a new table based of a base table with new primary keys and sort keys

Question 6

DynamoDB

Local Secondary Index

Answer 6

• this is used for queries which use the same partition key value
• maintains an alternate sort key for a given partition
• can only be added when a table is created
• local to the partition

Question 7

DynamoDB

Scan Operations

Answer 7

• less efficient than other operations
• always scan the entire or secondary index
• returns all the data attributes for the table
• supports filters

Question 8

DynamoDB

ProvisionedThroughputExceededExceptions

Answer 8

◦ Reasons: 
		‣ Hot Keys: one partition key is being read too much 
		‣ Hot Partitions: 
		‣ Large Items: 
◦ Solutions
		‣ Exponential back-off
		‣ Distribute the partitions keys are much as possible 
		‣ If RCU issue using DAX caching

Question 9

DynamoDB Stream Type: KEYS_ONLY

Answer 9

only the key attribute of the modified item are written

Question 10

DynamoDB Stream Type: NEW_IMAGE

Answer 10

the entire item after it was modified is written

Question 11

DynamoDB Stream Type: OLD_IMAGE

Answer 11

the entire item before it was modified is written to the stream

Question 12

DynamoDB Stream Type: NEW_AND_OLD_IMAGE

Answer 12

both new and old image are written to the stream