DynamoDB Interview Questions

• 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.

• Key-value stores
• Graph stores
• Column stores
• Document stores

• 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.

• 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.

• 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.

• 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.

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

• 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.

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.

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.

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

• Indexed Sort Key : The attribute on which indexing and querying are performed.
• Projected Attributes : It is the list of attributes from the table that can directly be copied into the local secondary index. Without projected attributes, the local secondary index contains only primary keys and secondary keys.

Currently, 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.