Crack Your AWS DynamoDB Interview: Top 10 Questions Answered
I’ve compiled a list of top 10 AWS DynamoDB interview questions and answers to help you prepare for your upcoming interviews:
- What is AWS DynamoDB?
AWS DynamoDB is a fully managed NoSQL database service offered by Amazon Web Services. It provides fast and predictable performance with seamless scalability. DynamoDB enables developers to store and retrieve any amount of data and serve any level of request traffic with low latency and high throughput.
- What are the key components of DynamoDB?
The main components of DynamoDB are tables, items, and attributes. A table is a collection of items, and each item is a collection of attributes. DynamoDB uses primary keys to uniquely identify each item in a table and secondary indexes to provide more querying flexibility.
- What are the differences between a primary key, partition key, and sort key in DynamoDB?
- Primary key: Uniquely identifies each item in a table. It can be a simple primary key (partition key) or a composite primary key (partition key and sort key).
- Partition key: The first part of a primary key, it determines the partition where the item is stored.
- Sort key: The second part of a composite primary key, it allows the items within a partition to be sorted for efficient querying.
- What is a Global Secondary Index (GSI) and a Local Secondary Index (LSI)?
- GSI: A global secondary index is an index with a partition key and an optional sort key that can be different from the base table’s primary key. GSIs span all partitions and support eventually consistent reads by default, but can also support strongly consistent reads.
- LSI: A local secondary index is an index that has the same partition key as the base table, but a different sort key. LSIs are only available on tables with composite primary keys and support strongly consistent reads.
- How does DynamoDB handle read and write consistency?
DynamoDB offers two types of read consistency: eventually consistent and strongly consistent. Eventually consistent reads provide better performance and availability, while strongly consistent reads guarantee that the read data reflects all writes that were successful up to a few seconds before the read request.
- What is the difference between Provisioned Throughput and On-Demand Capacity modes in DynamoDB?
Provisioned Throughput is when you set specific read and write capacity units for your table or index, while On-Demand Capacity mode allows DynamoDB to automatically manage the capacity based on the actual request traffic. On-Demand Capacity mode can be more cost-effective for workloads with unpredictable or highly variable traffic patterns.
- What is DynamoDB Streams?
DynamoDB Streams captures a time-ordered sequence of item-level modifications in a DynamoDB table and stores this data for up to 24 hours. You can use this data to build applications that react to changes in your table data or synchronize your table data with other data stores.
- How do you secure data in DynamoDB?
DynamoDB provides various security mechanisms, such as AWS Identity and Access Management (IAM) for controlling access, encryption at rest using AWS Key Management Service (KMS) for data protection, and VPC endpoints for secure communication within your VPC.
- What are the different backup and restore options available in DynamoDB?
DynamoDB offers two types of backups: on-demand backups and continuous backups with point-in-time recovery (PITR). On-demand backups allow you to create full backups of your table data and settings on demand, while PITR provides continuous backups of your table data, allowing you to restore your table to any point in time within the last 35 days.
- How can you monitor and optimize the performance of DynamoDB?
You can monitor and optimize the performance of DynamoDB using the following approaches:
AWS Management Console: The console provides an overview of key performance metrics, such as read and write throughput, latency, and error rates.
Amazon CloudWatch: CloudWatch allows you to monitor and set alarms on various DynamoDB metrics, such as read and write capacity, consumed capacity, throttling events, and more.
AWS Trusted Advisor: Trusted Advisor can provide recommendations on cost optimization, security, fault tolerance, and performance improvement for your DynamoDB tables.
Query Optimization: Optimize your queries by choosing the right primary keys and indexes, using filter expressions, and limiting the number of items fetched.
Provisioned Throughput Management: Monitor your table’s consumed capacity and adjust the provisioned throughput accordingly to avoid throttling or over-provisioning. Consider using auto-scaling to manage capacity automatically.
DynamoDB Accelerator (DAX): DAX is a fully managed, in-memory cache for DynamoDB that can significantly improve read performance, reduce latency, and decrease the load on your base table. It’s particularly useful for read-heavy or bursty workloads.
Data Compression: Consider compressing large attribute values before storing them in DynamoDB to reduce storage costs and improve I/O efficiency.
Global Tables: Use global tables to replicate your table data across multiple AWS regions for low-latency access and improved data durability.
Time-to-Live (TTL): Set a TTL attribute on your items to automatically expire and delete old data, reducing storage costs and improving overall performance.
Backup and Restore: Regularly perform backups and test your restoration process to ensure data durability and recoverability.
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