Interview Questions on AWS DynamoDB



Amazon-backed DynamoDB is a kind of NoSQL database that gives thrilling options like fast and extremely predictable efficiency, excessive reliability over knowledge, and seamless scalability. With the assistance of AWS DynamoDB, we will entrust the admin duties related to the distributed databases working and scaling. It’s an efficient knowledge storing and retrieval method that comes with totally different pricing tiers to go well with totally different buyer necessities and permit them to create tables for the database. Regardless of whether or not you’re a brisker or any technical knowledgeable, if you happen to’re making ready for AWS-offered positions, then that is the precise place you might be landed at. This weblog will enable you to to realize an understanding of DynamoDB and enable you to put together for twisted interview questions.

AWS DynamoDB | AWS |


Studying Targets

After studying this weblog totally, you’ll have the  confidence to reply interview questions on the next:

1. Overview of AWS DynamoDB, its function within the technical period, and why it’s wanted when now we have instruments like Aurora.

2. Insights into subjects like major keys in DynamoDB, world and native secondary indexes, knowledge pipeline, and projections in DynamoDB.

3. Information of AWS DynamoDB workflow together with totally different ideas like DynamoDB pricing tiers.

4. An understanding of DynamoDBMapper class together with its strategies like save, delete, question, depend, and many others.

5. Perceive how DynamoDB prevents knowledge loss in real-time, working of Question performance in DynamoDB, and many others.

This text was revealed as part of the Data Science Blogathon.

Desk of Contents

AWS DynamoDB Interview Questions for Freshers

Q1.  Can we use DynamoDB without cost?

The pricing system of AWS DynamoDB relies on the assets you provision. You can begin utilizing DynamoDB with the free tier limits of DynamoDB, the place many functions function. However, if you happen to require further assets, then there’s a pricing per 30 days system, which varies relying upon the kind of assets required.

Q2. What’s the most dimension of an merchandise in Amazon DynamoDB?

In DynamoDB, 400 KB is the perfect and most merchandise dimension; it incorporates each the attribute identify size in UTF-8 format in addition to the worth lengths in binary format.

Q3. Can DynamoDB help atomic updates in place?

Sure, DynamoDB helps the Fast in-place atomic notifications by permitting us to extend or lower the numeric attributes with a single API name in addition to so as to add or delete lists, units, or maps.

This autumn. Give the identify of 4 use circumstances of AWS DynamoDB.

  • Enterprise Intelligence(BI)
  • On a regular basis Net Analytics
  • Information Warehousing
  • Actual-time Analytics

Q5. Clarify two kinds of major keys utilized by DynamoDB.

AWS DynamoDB | AWS |


  • Partition Key: DynamoDB makes use of it to partition your knowledge into separate logical knowledge shards. To an inside hash operate, the partition key worth is inputted by DynamoDB, producing an output that can determine the partition (bodily storage inside to DynamoDB) through which location the merchandise will likely be saved.
  • Kind Key: The kind secret’s used to type all objects with the identical partition key worth to retailer them collectively. Used to find out storage location.

Q6. Clarify the 2 kinds of secondary indexes supported by Amazon’s DynamoDB.

AWS DynamoDB | AWS |


  • International Secondary Index: A worldwide secondary index consists of a partition key together with the type key that’s distinct from the first key of a base desk. It’s outlined as “International” as a result of queries on the index can cowl all of the objects in a base desk, together with all of the partitions.
  • Native Secondary Index: A neighborhood secondary index is an index with a distinct type key however the identical partition key as the first desk. It’s outlined as “native” as a result of queries on the index can cowl solely the bottom desk partition with the identical partition key worth.

Q7. What number of world secondary indexes are you able to create for every desk?

The utmost variety of world secondary indexes permitted to every desk is 5(5).

Q8. Can we erase the native secondary indexes?

As per the present situation, as quickly because the native secondary indexes are created, Amazon DynamoDB can’t take away them from the bottom desk; the one answer is to delete your entire desk.

Q9. Clarify the variations between Amazon DynamoDB and Amazon SimpleDB.

Amazon DynamoDB Amazon SimpleDB
It is rather Quick and scalable. It has Scaling limitations.
It helps to take care of excessive efficiency and to be extremely cost-effective for workloads. SimpleDB helps and attributes flexibility at the price of efficiency.

Q10. Identify totally different knowledge sorts supported by DynamoDB.

The scalar knowledge sorts provided by DynamoDB embody the next:

  • Boolean (Y/N)
  • Numbers (0-9)
  • Strings (alphanumerics)
  • Binary (0,1)

The info sorts for collections provided by DynamoDB embody the next:

  • String Set
  • Quantity Set
  • Heterogeneous Binary Set
  • Differentiated Map

Notice: Null values are additionally acceptable.

Q11. Is it attainable so as to add the native supplementary indexes to a desk that already exists within the database?

As quickly as we set up any desk to native secondary indexes, now we have the chance to outline a kind key aspect that’s presently unused to outline a neighborhood secondary index that can be utilized every time wanted.

This means that including native secondary indexes to the present desk is considerably inconceivable for now.

Q12. Give 5 methods to get knowledge from DynamoDB.

  • Question Technique
  • Scan Technique
  • GetItem Command
  • BatchGet Command
  • TransactRead Command

Q13. Clarify the Projections in DynamoDB.

Initiatives are the set of attributes which might be copied from the bottom desk to an index. This strategy of Projection will all the time happen together with the partition key and type key.

The minimal 3 attributes carried by every index embody:

A. Base desk’s type key worth

B. Base desk’s partition key worth

C. Attribute to function the index type key

Q14. Clarify the function of the information pipeline in DynamoDB.

The function of the Information Pipeline in DynamoDB is to export and import knowledge from the S3 bucket, present knowledge backup every time historical past knowledge is required, and carry out knowledge testing.

Two kinds of Information Pipeline embody:

A. DataPipelineDefaultRole: It carries all of the actions which might be permitted for the pipeline to carry out.

B. DataPipelineDefaultResourceRole:  It carries all of the assets which might be permitted for the pipeline to carry out.

Q15. How can we generate Entry Key and Secret Key in DynamoDB?

We will simply generate an entry key and secret key by Making a Consumer from Amazon’s Identification Entry Administration(IAM).

Interview Questions for Technical Consultants

Q1. Clarify the working of Amazon DynamoDB.

The working of AWS DynamoDB is kind of easy to grasp because it makes use of B-trees and Hashing strategies to handle advanced knowledge. To start with, after we enter the information, it makes use of a hashing method to get distributed into totally different partitions after which the information will get saved in a specific partition after initializing it with a key worth.

Workings | Interview questions


Every knowledge partition is able to dealing with 3000 reads and 1000 write models, together with a default storage capability of 10GB. The partition key values are utilized in DynamoDB to retailer and retrieve the data. Dynamo DB inserts the important thing worth to the hash operate to write down an merchandise to the desk after which makes use of the hash operate output to find out the partition location of the place the merchandise must be saved.

Q2. Clarify the idea of DynamoDBMapper class together with its strategies.

The DynamoDBMapper class is nothing however the entry level of DynamoDB that permits us to drag knowledge from numerous tables, scan tables, execute queries, carry out CRUD(Create, Learn, Replace, and Delete) operations, and provide entry to a DynamoDB endpoint.

public DynamoDBMapper(AmazonDynamoDB dyno,
                      DynamoDBMapperConfig configer)

This class is used to construct a brand new mapper with the given service object and configuration.

1. dyno- The identify of the service object is used to deal with all service calls.

2. config- It’s the identify of the default configuration that may be overridden on a per-operation foundation and used for all service calls.

The strategies of DynamoDBMapper class embody the:

A. getS3ClientCache: S3ClientCache is a great Map for AmazonS3Client objects and this operate returns the underlying S3ClientCache for accessing Amazon S3. S3ClientCache could be very helpful when now we have a number of shoppers, because it not solely retains the shoppers organized by AWS Area however can even create new Amazon S3 shoppers on demand.

public S3ClientCache getS3ClientCache()

B. Save: Because the identify suggests this operate saves the particular object to the desk and wishes no different parameter to cross. Though, we will additionally give some non-compulsory configuration parameters utilizing the DynamoDBMapperConfig object.

public <T> void save(T obj,
                     DynamoDBSaveExpression saveExp,
                     DynamoDBMapperConfig configer)


1. obj: The identify of an object that has to save lots of into DynamoDB.

2. saveExp: It defines the choices wanted to be utilized to save lots of the request.

C. Delete: Delete operate merely deletes the merchandise from the desk with the compulsion of passing the item occasion of the mapped class.

public <T> void delete(T obj,
                       DynamoDBDeleteExpression deleteExp,
                       DynamoDBMapperConfig configer)

D. Question: The question operate is used to question a desk or a secondary index however the compulsion is that the desk/index should have a composite major key (partition key and type key).

public <T> PaginatedQueryList<T> question(Class<T> cl,
                                       DynamoDBQueryExpression<T> queryExp,
                                       DynamoDBMapperConfig configer)


1. cl: cl represents the annotated class with AWS DynamoDB to inform the right way to retailer the item knowledge in AWS DynamoDB.

2. queryExp: It supplies the situations that should be placed on the important thing values in addition to the small print have to run the question.

E. scanPage: This operate scans a desk or secondary index and returns a single web page of matching outcomes however that return web page is the quantity of knowledge that matches inside 1 megabyte.

public <T> ScanResultPage<T> scanPage(Class<T> cl,
                                      DynamoDBScanExpression scanExp,
                                      DynamoDBMapperConfig configer)

F. queryPage: This operate is used to scan your entire desk or secondary index and we will additionally present the FilterExpression to filter the end result set however this function is completely non-compulsory.

public <T> QueryResultPage<T> queryPage(Class<T> cl,
                                        DynamoDBQueryExpression<T> queryExp,
                                        DynamoDBMapperConfig configer)

G. Depend: This operate evaluates the particular scan expression to search out the matching objects and returns them.

public <T> int depend(Class<T> cl,
                     DynamoDBQueryExpression<T> queryExp,
                     DynamoDBMapperConfig configer)

H. createS3Link: This operate is used to create a hyperlink to an object in Amazon S3, the place now we have to provide the bucket identify and a key identify to uniquely determine the item within the bucket.

public S3Link createS3Link(String s3region,
                           String b_Name,
                           String b_key)

Q3. Clarify the working of Question performance in DynamoDB.

AWS DynamoDB permits two kinds of knowledge fetching choices to fetch knowledge from collections: the Scan technique and the Question technique.

Query functionality | Interview questions

Supply: dynobase

1. Within the Scan technique, DynamoDB scans your entire desk and searches the information with its matching standards.

2. Within the Question technique, DynamoDB performs the direct lookup for a particular dataset with the assistance of key constraints. To enhance the learn/ write operation pace and the information flexibility, it makes use of not solely the first key but additionally a partition major key, a world secondary key, and a neighborhood secondary key.

That’s why the AWS DynamoDB question method is really useful for many knowledge fetching eventualities and its options like time efficient, quick pace, and many others., make it higher than the DynamoDB scan.

This autumn. Clarify the distinction between DynamoDB and Aurora.

AWS DynamoDB Aurora
AWS DynamoDB is a non-relational database administration system. Aurora is a relational database service.
It makes use of the specialised syntax of NoSQL to fetch and course of the information. It makes use of the Structured Question Language for performing the duties like knowledge manipulation and fetching.
Because the partitioning technique, it prefers the utilization of Sharding. It makes use of easy horizontal partitioning.
DynamoDB will be operated with the important thing worth in addition to doc fashions. It could solely be operated with relational databases.
DynamoDB doesn’t help server-side scripting. Aurora helps the scripting on the sever-side.

Q5. Clarify the idea of Auto Scaling in DynamoDB.

AWS DynamoDB wants Auto Scaling as a result of it will get very tough generally to inform beforehand in regards to the database’s workload. By Auto Scaling function DynamoDB is able to scaling the learn and write capability with respect to the visitors.

Auto scaling | Interview questions


The function of Scaling up permits world secondary indexes and the tables to realize extra learn and write and another choice of cutting down is confirmed as cost-effective as a result of it’s routinely primarily based on the visitors.

Q6. Clarify the 2 DynamoDB pricing tiers.

1. On-demand Capability Mode: The on-demand capability mode is a kind of pricing tier that’s ideally used for situations when the visitors is unpredictable. It scales the database cases by specializing in the incoming visitors to the applying.

2. Provisioned Capability Mode: The provisioned capability mode is a kind of pricing tier that’s ideally used for situations when the visitors is constant and predictable. It permits clients to decide on auto-scaling and specify the reads and writes per second.

Q7. Clarify how DynamoDB prevents knowledge loss in actual time.

DynamoDB has a two-tier backup system together with long-term storage, which ensures minimal knowledge loss in actual time. Mainly, every participant in DynamoDB has three nodes, and every node carries the identical knowledge from the partition to keep away from knowledge loss resulting from failure at one node. Other than that, to trace the modifications in every node for knowledge location and a replication log, AWS DynamoDB additionally has a B tree. A unique AWS database is used to retailer the snapshot of this knowledge virtually for a month in order that the information will be pulled out as quickly as requested.


This weblog covers many of the often requested DynamoDB interview questions that could possibly be requested in knowledge science, DynamoDB developer, Information Analyst, and large knowledge developer interviews. Utilizing these interview questions as a reference, you possibly can higher perceive the idea of DynamoDB and begin formulating efficient solutions for upcoming interviews. The important thing takeaways from this DynamoDB weblog are:

  1. AWS DynamoDB is a extremely managed NoSQL database service that gives efficient knowledge storing and retrieval strategies with totally different pricing tiers to go well with totally different buyer necessities.
  2. DynamoDB makes use of B-trees and Hashing strategies to handle advanced knowledge and helps each key-value and doc knowledge constructions.
  3. It permits two kinds of knowledge fetching choices, together with the scan and the question technique to fetch knowledge from collections.
  4. AWS DynamoDB provides a two-tier backup system and long-term storage to make sure minimal knowledge loss.

When you have any interview questions on this matter. Then, share them with me within the feedback beneath.

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