AWS DynamoDB

Question 1

What type of database is DynamoDB?

Answer 1

DynamoDB is a fully managed NoSQL database service that supports key-value and document data models.

Question 2

What are the main data structures used in DynamoDB?

Answer 2

Tables
Items (rows)
Attributes (columns).

Question 3

What are the primary keys in DynamoDB?

Answer 3

Partition key (hash key)
Partition key + Sort key (composite key).

Question 4

What is the maximum size of an item in DynamoDB?

Answer 4

400 KB per item.

Question 5

What read/write capacity modes does DynamoDB support?

Answer 5

Provisioned mode: Pre-defined read/write capacity units (RCUs/WCUs)
On-demand mode: Auto-scales based on traffic

Question 6

What are the consistency options for reads in DynamoDB?

Answer 6

Eventually consistent reads (default)
Strongly consistent reads

Question 7

How are read capacity units (RCUs) calculated?

Answer 7

Eventually consistent read: 1 RCU = 8 KB per second.
Strongly consistent read: 1 RCU = 4 KB per second.

Question 8

How are write capacity units (WCUs) calculated?

Answer 8

1 WCU = 1 write per second for an item up to 1 KB

Question 9

What types of indexes does DynamoDB support?

Answer 9

Primary index: partition key or composite key

Secondary indexes:
Global Secondary Index (GSI): any attribute, across partitions
Local Secondary Index (LSI): same partition key, different sort key

Question 10

Can you change a primary key after table creation?

Answer 10

No, you cannot change the primary key.
You must create a new table.

Question 11

What is DynamoDB Streams?

Answer 11

A time-ordered sequence of item-level changes in a table.
Used for replication, triggers, and analytics.

Question 12

What is DynamoDB TTL (Time to Live)?

Answer 12

TTL automatically deletes expired items based on a timestamp attribute.

Question 13

What is the maximum table size for DynamoDB?

Answer 13

DynamoDB tables scale virtually without limit.
You don’t manage partitions manually.

Question 14

How is high availability achieved in DynamoDB?

Answer 14

Through multi-AZ replication within a region
For cross-region, use Global Tables.

Question 15

What are DynamoDB Global Tables?

Answer 15

Fully managed, multi-region, multi-master tables for global applications.

Question 16

Can DynamoDB Global Tables automatically handle conflict resolution?

Answer 16

Yes, using last-writer-wins (timestamp-based) conflict resolution.

Question 17

How do you design a DynamoDB table for high throughput?

Answer 17

Use evenly distributed partition keys
Avoid hot partitions
Use GSIs/LSIs carefully to optimize queries

Question 18

How do you efficiently query large datasets?

Answer 18

Use Query instead of Scan wherever possible.
Use pagination for large results.

Question 19

What is Pagination in DynamoDB ?

Answer 19

Pagination is the process of retrieving large results sets in multiple smaller chunks (pages) instead of all at once.

Question 20

How do you handle unpredictable traffic spikes?

Answer 20

Use on-demand capacity mode or DAX caching

Question 21

How can you secure DynamoDB data?

Answer 21

IAM policies for table access
Encryption at rest using AWS KMS
TLS for in-transit encryption

Question 22

What is DynamoDB Accelerator (DAX)?

Answer 22

Fully managed, in-memory caching service for DynamoDB.
It reduces read latency from milliseconds to microseconds.

Question 23

Can DAX cache writes as well as reads?

Answer 23

No, DAX only accelerates read operations.
Writes go directly to DynamoDB.

Question 24

Which DynamoDB feature provides automatic deletion of expired items?

Answer 24

TTL (Time to Live)

Question 25

You need a table to store user sessions that expire after 30 minutes. Which features help?

Answer 25

TTL + On-demand capacity mode

Question 26

Your application needs a globally distributed, multi-master DynamoDB setup. Which feature should you use?

Answer 26

Global Tables

Question 27

You have a table with uneven traffic on certain partition keys. What is a potential solution?

Answer 27

Redesign partition keys to ensure even distribution. Consider write sharding

Question 28

How do you reduce read latency for frequently accessed DynamoDB items?

Answer 28

Use DAX caching