面试题与答案

DynamoDB is a fully managed NoSQL database service provided by AWS.

DynamoDB uses a key-value model where each item (record) in the database is uniquely identified by a primary key.

DynamoDB Local is a downloadable version of DynamoDB that enables local development and testing. It allows developers to test applications without incurring AWS costs.

The 'DeleteItem' operation removes one or more items from a table based on their primary key. It is used to delete specific items from a table.

The 'CreateTable' operation is used to create a new table in DynamoDB. It involves specifying the table name, primary key attributes, and provisioned throughput settings.

The 'DescribeTable' operation provides metadata about a table, including its schema, provisioned throughput settings, and the status of any secondary indexes.

Capacity Units represent the throughput that a table can handle. Read Capacity Units (RCUs) and Write Capacity Units (WCUs) determine the amount of read and write operations a table can support.

'ListTables' provides a list of all the tables in a given AWS account and region. It does not require the use of the table's primary key.

'PutItem' creates a new item or replaces an existing item with a new one. It adds an item to the table if it does not exist, or replaces the existing item if it does.

'DeleteTable' is used to delete an existing table and all of its data permanently. Once deleted, a table cannot be recovered.

'GetItem' retrieves a single item from a table based on its primary key. It is used to read a specific item from the table.

DynamoDB supports two types of primary keys: partition key and composite key (partition key + sort key).

Provisioned Throughput is the capacity (read and write) reserved for a table. It ensures predictable performance.

DynamoDB is a NoSQL database with a flexible schema, automatic scaling, and high availability, while traditional relational databases are SQL-based with a fixed schema.

DynamoDB achieves scalability and high availability through partitioning, replication, and automatic sharding of data across multiple servers.

Consistent Read ensures that a read operation returns the most up-to-date data reflecting all writes that are acknowledged before the read.

A Local Secondary Index is an index that has the same partition key as the base table but a different sort key. It allows efficient querying of data within a single partition.

An Item Collection is a set of items that have the same partition key value in a table with a composite primary key. Collections are formed when a table has a sort key.

DynamoDB uses conditional writes and optimistic concurrency control to handle conflicts in write operations. Conditional writes allow you to specify conditions for write operations to succeed.

TTL is a feature in DynamoDB that allows you to automatically expire items from a table after a specified time. It is useful for managing data that has a limited lifespan.

DynamoDB Streams capture changes to items in a table, including new items, updates, and deletions. It allows you to process and react to changes in real-time.

DynamoDB is schema-less, allowing you to add or remove attributes at any time without affecting existing items. Indexes need to be created or modified separately.

The 'Scan' operation in DynamoDB reads every item in a table, making it less efficient than 'Query.' It should be used sparingly and is often used when a table has no defined schema.

DynamoDB provides both eventual and strong consistency. By default, read operations are eventually consistent, but you can request strongly consistent reads when needed.

'BatchGetItem' retrieves multiple items from one or more tables using their primary keys. It allows efficient retrieval of multiple items in a single request.

'UpdateItem' modifies existing attributes or adds new ones to an existing item, while 'PutItem' creates a new item or replaces an existing item with a new one.

The 'Query' operation retrieves items from a table using a specified primary key or index key. It is more efficient than 'Scan' for retrieving a subset of items.

Conditional Writes allow you to specify conditions that must be satisfied for a write operation to succeed. It helps in avoiding conflicts and ensuring data integrity.

DynamoDB uses AWS Identity and Access Management (IAM) to control access to tables. You can define fine-grained access policies to control who can perform specific actions.

'BatchWriteItem' writes multiple items to one or more tables using a single request. It is more efficient than making individual 'PutItem' or 'DeleteItem' calls.

PITR allows you to restore a table to any point in time within the last 35 days. It helps in recovering from accidental data loss or corruption.

DynamoDB encrypts data at rest using AWS Key Management Service (KMS) and supports encrypted connections (SSL/TLS) for data in transit.

'UpdateTable' is used to modify the provisioned throughput settings for a table. It can be used to increase or decrease the capacity of a table.

DynamoDB supports on-demand backups and enables Point-in-Time Recovery (PITR). Backups can be used to restore a table to any point in time within the last 35 days.

'BatchGetItem' retrieves multiple items from one or more tables using their primary keys. It allows efficient retrieval of multiple items in a single request.

A Global Secondary Index allows querying a table based on alternate keys in addition to the primary key. It provides more flexibility in querying data.

On-Demand Throughput allows you to pay per request without capacity planning, while Provisioned Throughput requires capacity planning and offers cost savings for consistent workloads.

Best practices include choosing the right primary key, using appropriate read and write capacities, avoiding hot keys, and utilizing secondary indexes judiciously.

DAX is an in-memory caching service that provides fast read access to frequently accessed data in DynamoDB, reducing the need to read from the DynamoDB table directly.

Provisioned Concurrency is a feature that ensures that a specified number of read and write capacity units are always available for your table, reducing warm-up times.

Auto Scaling automatically adjusts the provisioned read and write capacity based on the actual usage of a table. It helps in handling varying workloads.

Limitations include a maximum item size of 400 KB, a maximum of 256 tables per region per account, and a maximum provisioned capacity of 40,000 read and write capacity units.

DynamoDB is a NoSQL database service, while Amazon RDS is a relational database service. DynamoDB is designed for scalability and high availability, while RDS offers traditional relational database features.

'TransactWriteItems' allows you to perform multiple write operations as a single, atomic transaction. Either all the operations in the transaction succeed, or none of them are applied.

DAX provides low-latency read access to DynamoDB tables by caching frequently accessed data. It reduces the need to read from the DynamoDB table directly, improving application performance.

DynamoDB supports transactions using the 'TransactWriteItems' operation. It allows you to group multiple write operations into a single, atomic transaction.