AWS DynamoDB Interview Questions

A managed NoSQL database service, Amazon DynamoDB offers quick and predictable performance along with seamless scalability. By using DynamoDB, you can delegate the administrative tasks associated with running and scaling a distributed database, freeing you from having to worry about hardware provisioning, setup, software patching, replication or cluster scalability. Additionally, DynamoDB provides encryption at rest, which removes the operational complexity and burden of protecting sensitive data.

Now that you know what AWS DynamoDB is, let us learn some less-known facts about it:

• You can create a new DynamoDB table and import data directly from Amazon S3 without creating any code or trying to manage any additional infrastructure.
• DynamoDB is supported by AWS Glue Elastic Views as a source to continuously integrate and replicate data across various databases in almost real-time.
• To query, update, insert and delete table data in DynamoDB, use the PartiQL query language.
• You can record item-level changes in the DynamoDB tables using Amazon Kinesis Data Streams.
• Even more quickly restore DynamoDB tables.
• DynamoDB is now supported by the AWS Pricing Calculator.
• Export your DynamoDB data to Amazon Simple Storage Service (Amazon S3), then use Amazon Athena and other AWS services to analyze the data and derive useful insights.

The demand for AWS DynamoDB is quite high and therefore, the opportunities are quite vast. We assure you that the interview questions will assist you in acing the interview and getting the dream job and role.

We have categorized AWS DynamoDB Interview Questions into 3 levels they are:

• Freshers
• Experienced
• FAQs

Frequently Asked AWS DynamoDB Interview Questions

1. What sort of query functionality is supported by DynamoDB?
2. What are the APIs provided by Amazon DynamoDB?
3. What kinds of secondary indexes does Amazon's DynamoDB support?
4. How can local secondary indexes be made?
5. Redis: Is it quicker than DynamoDB?
6. What are a few applications of DynamoDB?
7. How well do you comprehend DynamoDB Streams?
8. Can DynamoDB be used to access data kept in AWS S3?
9. What do you think about Firebase vs DynamoDB?
10. What do you think the eventual consistency model means?

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AWS DynamoDB Interview Questions For Freshers

1. What are the data types supported by DynamoDB?

The four scalar data types that DynamoDB supports are as follows:

• Numbers
• Strings
• Binary
• Boolean.

Data types for collections that DynamoDB supports include:

• String Set Number Set
• Heterogeneous Binary Set
• Differentiated Map
• DynamoDB accepts Null values.

2. Can DynamoDB perform atomic updates in place?

Quick in-place atomic notifications are supported by Amazon DynamoDB, allowing you to add or eliminate lists, sets or maps while also incrementing and decrementing a numeric attribute with just one API call.

3. What sort of query functionality is supported by DynamoDB?

• GET/PUT operations that use the user-defined unique identifier are supported.
• By enabling querying of a non-primary key characteristic using both local and global secondary indexes, it offers flexible querying.
• Data for an item linked to a single attribute separation primary key can be read and written quickly.
• It enables you to access all the items for a single aggregate partition-sort key along a number of sort keys using the Query API.

4. Is conditional operation support available for Amazon DynamoDB?

You must specify a condition in order for a procedure to be finished on an item. A condition expression which can be created from the following is one you can define:

• Comparison operators: =, >,, >, =, >, BETWEEN, and IN Logic operations: NOT, AND, and OR Boolean functions: ATTRIBUTE EXIST, CONTAINS, and BEGINS WITH
• You can also create a conditional expression that is free-form and combines several conditional clauses, including nested clauses.

5. What are some of the differences between Amazon SimpleDB and Amazon DynamoDB?

Crafted for internet application domains, Amazon DynamoDB is a quick and scalable NoSQL database provider that is also highly recommended. It maintains predictable high performance and is extremely cost-effective for caseloads of any scale. 

Although it has scaling restrictions, Amazon SimpleDB is a good choice for smaller caseloads that demand query flexibility.

At the expense of performance and scale, it supports query flexibility and instantaneously indexes all item attributes.

6. What are the APIs provided by Amazon DynamoDB?

• UpdateTable
• CreateTable
• DescribeTable
• DeleteTable
• PutItem
• ListTables
• UpdateItem
• BatchWriteItem
• GetItem
• Query
• DeleteItem
• Scan
• BatchGetItem.

7. Could you please define global secondary indexes?

The term "global Secondary index" refers to an index with a partition and divided key that differs from those on the table.

In the context that questions on the index could indeed cover every item in a table throughout all partitions, it is regarded as being "global."

8. What kinds of secondary indexes does Amazon's DynamoDB support?

Amazon DynamoDB supports a pair of index types. As follows:

• A global secondary index is one that has a partition or partition sort key that really is distinct from the table's primary key. Because questions on the index can cover all the items in a table across all the partitions, it is referred to as a global secondary index.
• Local secondary index: An index with a different sort key than the table's partition key. Since every index partition is bound to a table partition with the same partition key, it is regarded as being "local."

9. How can a Global Secondary Index be removed from Amazon DynamoDB?

The console or an API call can be used to remove a Global Secondary Index.

• The Global Secondary index can be removed from a table by selecting it on the console, going to the "Table items" section and choosing the "indexes" tab, and then clicking the "Delete" button next to the delete index.
• The Notification Table API call can also be used to delete a Global Secondary Index.

[ Learn Complete about Amazon Web Services Console ]

10. How many global secondary indexes are created for each table?

Per table, a maximum of 5 global associated increases are permitted.

11. What types of API calls does a global secondary index support?

The API calls that Global Secondary Index supports are "Query" and "Scan."

12. On how many different tables can local secondary indexes be created?

There can be a maximum of five local associated increases per table.

13. Are local secondary indexes erasable?

Currently, once local secondary indexes are created, Amazon DynamoDB is unable to remove them from the table; however, the entire table can be deleted.

14. A table that already exists can I add local supplementary indexes to?

Once you establish a table to local secondary indexes, you can define a sort key element that isn't currently used to set up a local secondary index for use in the future.

This means that adding local secondary indexes to the existing table is likely impossible right now.

15. How can local secondary indexes be made?

• When making a table that can't be added right now, a Local secondary index must be created.
• You should therefore try specifying the two following parameters later on when you establish a local secondary index.
• The characteristic about which indexing and query processing are done is known as an indexed sort key.
• Attributes that can be directly copied into the school serves index are known as projected attributes. The local secondary index only contains primary keys and secondary keys when projected attributes are absent.

16. What exactly are projects?

The group of characteristics which are copied or predicted from a table to an index are called projections. They are in addition to the automatically projected index key attributes and primary key attributes. The characteristics that are estimated into the index must always be specified when defining a local secondary index. Each index has a minimum of three of the following attributes:

• Table segment key value
• To be used as the index sort key attribute
• Table key-value sort.

17. What sort of query functionality is supported by DynamoDB?

It supports GET/PUT operations using the user-specified primary key. The ability to query a non-primary key attribute using both local and global secondary indexes promotes flexible querying.

18. Redis: Is it quicker than DynamoDB?

• Inserts/Delete are extremely quick because DynamoDB is a NoSQL database.
• DynamoDB permanently stores data (although it is less fast than Redis because we don't need that much speed).

19. Are writes to DynamoDB Atomic?

Atomic counters are a feature of DynamoDB that let you change the value of an established attribute without affecting other write requests by using the update method. It increases the value of this characteristic by one each time the programme is executed.

AWS DynamoDB Interview Questions For Experienced

20. What are the main advantages of using DynamoDB over an established MySQL-style SQL-based database?

Several advantages of DynamoDB over conventional SQL databases. You don't have to worry about providing or managing servers because it is a completely managed service. Second, you could indeed quickly increase or decrease ability as needed because it is highly scalable. Finally, you can be sure that your data is secure because it has built-in compliance and security features.

21. How is Amazon's NoSQL implementation different from other well-known ones like Cassandra or MongoDB?

A managed NoSQL database service, DynamoDB provides quick, predictable performance with easy scalability. Several significant aspects set DynamoDB apart from other well-liked NoSQL implementations:

• DynamoDB provides a managed service rather than needing setup and management by the user.
• DynamoDB utilizes a proprietary query language rather than SQL, DynamoDB employs a proprietary storage format rather than JSON.

22. What are a few applications of DynamoDB?

Any application that requires latency access to data and is willing to give up some data modeling flexibility in exchange for performance should consider DynamoDB. Additionally, it is a wise choice for programs that need to be highly available and are willing to give up some performance to achieve it.

23. Do you have any restrictions when using DynamoDB? If so, what exactly are they?

Although DynamoDB is a strong tool, it does have some drawbacks. Its inability to handle large amounts of information is one of its limitations. You might want to think about a different solution if you need to store a lot of data. You should compare the costs of using DynamoDB with the advantages it offers because it can be costly to use.

24. What different methods are there for accessing data in DynamoDB?

The Query or Scan APIs can be used to access data stored in DynamoDB. The Scan API enables you to browse through data for items that meet specific criteria, whereas the Query API enables you to ask a series using a primary key.

25. How well do you comprehend DynamoDB Streams?

You can record data changes in one's DynamoDB table in almost real-time using DynamoDB Streams, a feature of DynamoDB. This can be helpful for a variety of purposes, such as auditing or maintaining a backup copy of your data in a different location for disaster recovery.

26. What functions are carried out by DynamoDB Streams?

You can record data adjustments done to goods in a DynamoDB table using a feature called DynamoDB Streams. Then, you can take action with that data by retrieving, filtering, or trying to export it to a different DynamoDB table, among other actions.

27. Can DynamoDB be used to access data kept in AWS S3?

It is possible to use DynamoDB to connect data stored in AWS S3. But to do that, you'll need to use an API designed specifically for DynamoDB.

28. Could you provide me with a few instances of real-world applications that employ the use of DynamoDB as their main database?

The Amazon.com website, the Kindle Fire tablet line, and the Amazon Web Services cloud computing service are a few real examples of applications that use DynamoDB as their main database.

29. What do you think about Firebase vs DynamoDB?

If you're going to look for a controlled NoSQL database that scales well, DynamoDB is a fantastic choice. Additionally, if you require precise control over your data, it is a wise choice. If you want a controlled NoSQL database that is feature-rich and simple to use, Firebase is a good choice.

[ Related Article: MongoDB vs DynamoDB ]

30. What do you know about DynamoDB's partition keys and sort keys?

Sort credentials are used to choose the order wherein items are kept within a partition, while separation keys are used to ascertain what partition an item would be stored in. A DynamoDB table can be searched for items using separation keys and sort keys combined.

31. What do you know about DynamoDB's local secondary indexes?

The capacity to query the DynamoDB data using a different sort key from the one used to shop the data in the table is provided by local secondary indexes. If you want to query the data in a variety of ways or if you need to, this can be helpful.

32. What do you think provisioned throughput means?

DynamoDB's provisioned throughput feature enables users to specify the read and write capacity needs for their table. The user can then make sure that one‘s table can accommodate the volume of traffic they anticipate.

33. What do you think the eventual consistency model means?

A technique for making sure that all duplicates of a data item are updated is the eventual consistency model. In distributed applications, where it may take some time for adjustments to reach every node, it is frequently used. According to the eventual consistency model, if enough time passes, all copies of a data item will have been updated.

34. What transpires if an application tries to read or write so many requests per second than is permitted?

Applications will encounter errors if they try to read or write greater than the maximum number of request units per second allowed. The application will need to increase its allotted request units or decrease the number of queries it is currently making.

35. Can you describe how conditional writes are used by DynamoDB to enhance performance?

By enabling you to clearly state conditions on write operations that need to be met in order for the write to be successful, DynamoDB uses conditional writes to help enhance efficiency. By doing this, you can prevent overwriting data which has already been revised by another process or writing duplicate data.

Advantages of AWS DynamoDB

• Scalable: Virtually unlimited storage allows users to store as much data as necessary
• Cost-effectiveness: It appears to be reducing costs while allowing a sizable portion of data to move from SQL to NoSQL. Basically, it charges for data reading, writing, and stashing as well as any optional DynamoDB features you decide to enable.
• Replication of data: Replication of data is either internally managed throughout multiple availability zones in a region or it may be made available across multiple regions. All data items are stored on SSDs.
• DynamoDB scales horizontally without a server by expanding a single table across several servers.
• Simple Administration: Because Amazon DynamoDB is a fully managed service, you don't have to worry about setting up and configuring hardware or software, applying software patches, managing distributed database clusters.

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Most Common AWS DynamoDB FAQs

1. What is AWS DynamoDB?

It is a NoSQL database provider that is well-designed, offers quick and unavoidable performance, and scales easily. Additionally, it allows users to delegate running and scaling online digital content distribution to AWS for the users' convenience, so they won't need to worry about setup, configuration, hardware requirements, replication, bandwidth capacity planning, cluster scaling, or software patching.

2. What are the benefits of AWS DynamoDB?

The following is a list of some advantages of using Amazon DynamoDB:

• It is a managed service, so there is no need to employ professionals or stress about setup, installation, clustering, etc.
• It can be scaled.
• Users can access it with high throughput and very little latency.
• It is strong and widely accessible.
• It is adaptable and enables the creation of dynamic tables with multi-valued attributes.
• It is economical.

3. What are non-relational databases?

The NoSQL databases used in non-relational databases. These databases are divided into four groups, which are as follows:

• Key-value registries
• Stores in graphs
• Stores in columns
• document archives.

4. Is AWS DynamoDB free?

You just pay for the assets you provision in Amazon DynamoDB. Start out with DynamoDB's free tier limitations, which power many applications. Depending on the kind of resources you need, there are different monthly prices when you're in need of them.

5. What is DynamoDB Mapper class?

It serves as DynamoDB's entry point. The DynamoDB Mapper class allows users to connect to a DynamoDB endpoint, allowing them to execute questions and scan against tables as well as carry out CRUD operations on items and access their data in various tables.

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6. What are key-value stores?

It is a database service that offers and facilitates the storing, updating, and querying of objects that are recognised using key and value pairs and make up the actual material that is being stored.

7. Explain DynamoDB auto-scaling.

Using DynamoDB, a global value with respect or a DynamoDB can automatically scale up and down in terms of read and write capacity.

8. Explain what DynamoDB BatchWriteItem does.

Multiple items all over multiple tables can be added, removed, or replaced using the Amazon DynamoDB BatchWriteItem in just one request, but not in a single transaction. It supports inserting or deleting combinations of up to 25 items with a total combined request size of 16 MB.

9. How are DynamoDB Access Key and Secret Key generated?

You can generate an access key and a secret key by creating a user in AWS IAM which is Identity Access Management.

[ Learn More About AWS IAM ]

10. Is DynamoDBMapper safe for threads?

It is possible to share this class across threads and it is thread-safe. DynamoDBMapper will start chucking DynamoDBMappingException while using the load, save and delete methods to demonstrate that domain courses are incorrectly marked or otherwise incompatible with this class.

Key Upshots

Key-value and document data models are supported by the NoSQL database Amazon DynamoDB. The use of DynamoDB by developers allows them to create serverless, modern applications that can scale globally and support petabytes of data as well as tens of millions of read and write requests per second. High-performance, internet-scale applications that would tax conventional relational databases can run on DynamoDB.