DynamoDB Interview Questions for Freshers/DynamoDB Interview Questions and Answers for Freshers & Experienced

Can I Add Local Secondary Indexes To An Existing Table?

When you create a desk with local secondary indexes, you may create a local secondary index to apply it in future by defining a sort key element which isn't always used presently.
So, presently it is probably not feasible to add nearby secondary indexes within the current desk.

What Are Projections?

Projections are the set of attributes which might be copied or projected from the desk to an index.
They are further to the index key attributes and primary key attributes which might be routinely projected.
Whenever you outline a nearby secondary index, it's miles required to specify the attributes which might be projected into the index.
Each index includes not less than 3 attributes. They are:Table partition key fee
Attribute to function the index type key
Table sort key fee.

What Are Local Secondary Indexes?

An index with the equal partition key because the table but special sort secret is known as nearby secondary index.
A local secondary index is considered to be “nearby” because every partition of a neighborhood secondary index is scaled to a desk partition which incorporates the identical partition key.

How To Delete A Global Secondary Index In Amazon Dynamodb?

A Global secondary index may be deleted from the console or through an API call.
Select the desk from that you want to delete the Global Secondary index at the console, pick the “indexes” tab underneath “Table gadgets” after which click on on the “Delete” button that is subsequent to the delete index.
A Global Secondary Index can also be deleted using the Update Table API name.

How Many Numbers Of Global Secondary Indexes Do You Create Per Table?

You are allowed to create a maximum of 5 international secondary indexes according to desk.

What Are Global Secondary Indexes?

An index with a unique partition and partition-and-kind key from those at the table is known as international Secondary index.
It is taken into consideration to be “worldwide” in the experience that queries on the index can span all of the objects in a table across, all the walls.

What Amazon Dynamodb Batchwriteitem Api Does?

The Amazon DynamoDB BatchWriteItem inserts, deletes and replaces a couple of gadgets throughout a couple of tables in just one request, however now not in a single transaction.
With maximum general request length of sixteen MB, it helps batches of up to twenty-five items to insert or delete.

List Some Difference Between Amazon Dynamodb And Amazon Simpledb?

Amazon DynamoDB :It is a fast and scalable NoSQL Database Service this is designed for internet scale applications, to maintain predictably excessive overall performance and to be quite fee-powerful for workloads of any scale, at the pinnacle of all it is particularly recommended.Amazon SimpleDB :It has scaling barriers and is a great in shape for smaller workloads that calls for question flexibility.It automatically indexes all object attributes and supports question flexibility on the cost of overall performance and scale.

How do you generate Dynamo DB Access key and Secret key?

* Log in to AWS and then go to the security credentials page.
* Navigate to Access Keys section then create a new access key by clicking on Create New Access Key.
* Click on the Show access key link to see the access key which was created.

What are the two types of primary keys supported by Dynamo DB?

* Partition key: Used for hash value to detect storage.

* Sort key: Used to detect storage location.

What does Data Pipeline do?

Data Pipeline exports and imports data from S3 bucket, file, etc.It also helps in backups, testing, and for similar needs.
There are 2 types Data Pipeline:
DataPipelineDefaultRole - contains all the ations you permit the pipeline to perform.
DataPipelineDefaultResourceRole - contains all the resources you permit the pipeline to perform.

Can I delete local secondary indexes?

Currently, the Amazon DynamoDB is incapable of removing the local secondary indexes from the table once they are created, but it is possible to delete the entire table.

How many local secondary indexes can be created on one table?

Each table can constitute up to five local secondary indexes.

Can I add local secondary indexes to an existing table?

When you create a table with local secondary indexes, you can create a local secondary index to use it in future by defining a sort key element which is not used currently.
So, at this time it is probably not possible to add local secondary indexes in the existing table.

What is the DynamoDB max item size?

400 KB is maximum item size in DynamoDB , which includes both attribute name binary length (UTF-8 length) and attribute value lengths (again binary length). The attribute name counts towards the size limit.

What is burst balance in RDS?

The burst balance relates to disk usage on your RDS instance. This assume you're using a GP2 volume which is bustable (it has credits that can be depleted too). Just like burstable instance classes ( T2 / T3 ) GP2 has a balance of available credits in which its IOPs can reach upto 3000 PIOPs.

What is Eventual Consistency?

According to Wikipedia, Eventual consistency is a consistency model used in distributed computing to achieve high availability that informally guarantees that, if no new updates are made to a given data item, eventually all accesses to that item will return the last updated value.

What is use of Scan operation in DynamoDB?

A Scan operation in Amazon DynamoDB reads every item in a table or a secondary index. By default, a Scan operation returns all of the data attributes for every item in the table or index. You can use the ProjectionExpression parameter so that Scan only returns some of the attributes, rather than all of them.

Are DynamoDB writes Atomic?

DynamoDB allows atomic counters, in which it uses the update method to increment or decrement the value of an existing attribute without interfering with other write requests. Each time it runs the program, it increments this attribute by one.

Does DynamoDB support in place atomic updates?

Amazon DynamoDB supports fast in-place updates. You can increment or decrement a numeric attribute in a row using a single API call. Similarly, you can atomically add or remove to sets, lists, or maps.

How do NoSQL databases like Dynamo different from SQL databases?

The relational model databases stores data into tables further dividing them into rows and columns. It defines rows and columns, indexes, the relationship between tables, and other database elements. On the other hand, NoSQL databases like Dynamo use various data models like key-value documents and graphs for retrieving and managing data.

Is DynamoDBMapper thread safe?

This class is thread-safe and can be shared between threads. While using the save, load, and delete methods, DynamoDBMapper will throw DynamoDBMappingException to show that domain classes are incorrectly annotated or otherwise incompatible with this class.

What is DynamoDB Auto Scaling?

DynamoDB is a superintended feature that scales up and down the read and write capacity of a DynamoDB or a global secondary index automatically.

Please explain key-value store?

It is a database service that provides and supports storing, updating and querying the objects that are identified using key and values that constitutes the actual content that is being stored.

What is the secondary indexes in DynamoDB?

A secondary index is a data structure that contains a subset of attributes from a table, along with an alternate key to support Query operations. You can retrieve data from the index using a Query , in much the same way as you use Query with a table.

How to generate DynamoDB Access Key and Secret Key?

By Creating User from AWS IAM (Identity Access Management), will be able to generate access key and secret key.

What are Projections?

Projections are the set of attributes that are copied or projected from the table to an index.
They are in addition to the index key attributes and primary key attributes which are automatically projected.

Whenever you define a local secondary index, it is required to specify the attributes that are projected into the index.

Each index consists of a minimum of 3 attributes, and they are:

* Table partition key value
* Attribute to serve as the index sort key
* Table sort key value

What are local secondary indexes?

An index with the same partition key as the table but different sort key is called local secondary index.
A local secondary index is considered to be “local” because every partition of a local secondary index is scaled to a table partition which contains the same partition key.

How to delete a Global Secondary Index in Amazon DynamoDB?

A Global secondary index can be deleted from the console or through an API call.
Select the table from which you want to delete the Global Secondary index on the console, select the “indexes” tab under “Table items” and then click on the “Delete” button which is next to the delete index.

A Global Secondary Index can also be deleted using the Update Table API call.

What are API calls supported by a global secondary index?

“Query” and “Scan” are the API calls that are supported by Global Secondary Index.

How many numbers of global secondary indexes do you create per table?

You are allowed to create a maximum of 5 global secondary indexes per table.

List types of secondary indexes supported by Amazons DynamoDB?

Two types of indexes are supported by Amazon DynamoDB. They are:
Global Secondary index – It is an index with a partition or a partition sort key that is different from those on the table. The global secondary index is considered to be global because queries on the index can span all the items in a table, across all the partitions.
Local secondary index – An index that has the same partition key as that of the table but different sort key. It is considered to be “local” because every partition of the index is scoped to a table partition that has the same partition key.

Please explain what are global secondary indexes?

An index with a different partition and partition-and-sort key from those on the table is called global Secondary index.
It is considered to be “global” in the sense that queries on the index can span all the items in a table across, all the partitions.

What is DynamoDB Auto Scaling?

DynamoDB is a superintended feature that scales up and down the read and write capacity of a DynamoDB or a global secondary index automatically.

Please explain key-value store?

It is a database service that provides and supports storing, updating and querying the objects that are identified using key and values that constitutes the actual content that is being stored.

What Amazon DynamoDB BatchWriteItem API does?

The Amazon DynamoDB BatchWriteItem inserts, deletes and replaces multiple items across multiple tables in just one request, but not in one transaction.
With maximum total request size of 16 MB, it supports batches of up to 25 items to insert or delete.

List the APIs provided by Amazon DynamoDB?

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

List some difference between Amazon DynamoDB and Amazon SimpleDB?

* Amazon DynamoDB : It is a fast and scalable NoSQL Database Service that is designed for internet scale applications, to maintain predictably high performance and to be highly cost-effective for workloads of any scale, on the top of all it is highly recommended.

* Amazon SimpleDB : It has scaling limitations and is a good fit for smaller workloads that requires query flexibility.It automatically indexes all item attributes and supports query flexibility at the cost of performance and scale.

What are advantages of DynamoDB?

1. Scalable - Unlimited amounts of data can be stored.
2. Distributed - DynamoDB scales horizontally by expanding a single table over multiple server.
3. Cost Effective - One year free tier provides more than 40 million database operations/month and pricing is based on throughput (read/write per second) than just storage.
4. Easy Administration - Fully managed service from Amazon.
5. Automatic data replication - All data items are stored on Solid State Disks (SSDs) and automatically replicated across multiple availability zones in a region.
6. Secure - DynamoDB security is better and is usually supported by the security measure provided by AWS. In order to authenticate users and prevent unauthorised data access, it uses proven secure techniques.

Is DynamoDB free for use?

Amazon DynamoDB is a fully managed NoSQL licensed database.
You can start with free tier limits of DynamoDB on which many applications runs.
If services are required, the price per month varies depending on the type of resources you need.

Is DynamoDB a SQL?

DynamoDB is NoSQL database, it can handle structured or semi structured data, including JSON documents. DynamoDB scales to accommodate very large amounts of data and very large number of users seamlessly.
SQL is the standard for storing and retrieving data. Relational databases have a wide range of tools available for simplifying the development of database-driven applications, however all of these tools uses SQL.

Does Amazon DynamoDB support conditional operations?

For an operation to be completed on an item, you have to specify a condition.
You can define a ConditionExpression that can be constructed from the following:

>> Boolean functions: ATTRIBUTE_EXIST, CONTAINS, and BEGINS_WITH
>> Comparison operators: =, <>, <, >, <=, >=, BETWEEN, and IN
>> Logical operators: NOT, AND, and OR.

You can also construct a free-form conditional expression that combines multiple conditional clauses which also includes nested clauses.

What kind of query functionality does DynamoDB support?

* It supports GET/PUT operation using the user-defined primary key.
* It provides flexible querying by letting query a non-primary key attribute using local secondary indexes and Global secondary indexes.
* It allows quick reads and writes data for an item associated with single attribute partition primary key.
* It allows you to use the Query API to retrieve all the items for a single composite partition-sort key across a range of sort keys.

Does DynamoDB support in-place atomic updates?

Amazon DynamoDB supports quick in-place atomic updates, where the numeric attribute’s increment and decrement can be done in arrow using just one API call or similarly, you can add or remove sets, lists, or maps.

List the Data Types supported by DynamoDB?

DynamoDB supports four scalar data types, and they are:

* Number
* String
* Binary
* Boolean

DynamoDB supports collection data types such as:

* Number Set
* String Set
* Binary Set
* Heterogeneous List
* Heterogeneous Map
* DynamoDB also supports Null values.

Explain what is DynamoDB Mapper Class?

It is the entry point to DynamoDB.The DynamoDB Mapper class provides access to a DynamoDB endpoint and enables the user to access to their data in various tables, execute queries and scan against tables, and perform CRUD operations on items.

Is DynamoDB free for use?

In Amazon DynamoDB you only pay for the resources you provision.
Get started with free tier limits of DynamoDB on which many applications operate.
In need of resources, the pricing per month varies depending on which type of resources you require.

What are the non-relational Databases?

The Non-Relational databases are NoSQL databases.
These databases are categorized into four groups, and they are:
* Key-value stores
* Graph stores
* Column stores
* Document stores

List some benefits of using Amazon DynamoDB?

Here is the list of some of the benefits of using Amazon DynamoDB:
* It is a managed service where there is no need to hire the experts or worry about installation, setup, cluster etc.,
* It is scalable.
* It provides the users high throughput at very low latency.
* It is durable and highly available.
* It is flexible and allows dynamic tables creation that includes multi-valued attributes.
* It is cost-effective.

what is DynamoDB?

It is a NoSQL database service which is superintended and provides fast and inevitable performance with seamless scalability.
It also enables the users to offload the operating and scaling distributed databases to AWS.
So that the users don’t have to worry about setup and configuration, hardware provisions, replication, throughput capacity planning, cluster scaling or software patching.

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