DynamoDB Streams Interview Questions and Answers for experienced

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DynamoDB Streams Interview Questions and Answers

  1. What are DynamoDB Streams?

    • Answer: DynamoDB Streams are a serverless feature that captures a continuous, ordered stream of changes to your DynamoDB tables. These changes include INSERT, UPDATE, and DELETE operations. Streams allow you to build applications that react to data changes in real-time, such as building audit trails, creating materialized views, or triggering downstream processes.

  2. What are the different stream view types available in DynamoDB Streams?

    • Answer: DynamoDB Streams offer two view types: `NEW_IMAGE` and `NEW_AND_OLD_IMAGES`. `NEW_IMAGE` only contains the new item after the modification. `NEW_AND_OLD_IMAGES` includes both the old and new item states, allowing you to track the changes made.

  3. Explain the concept of shards in DynamoDB Streams.

    • Answer: A DynamoDB stream is divided into shards. Each shard represents a partition of the stream, and changes are written to specific shards based on the table's hash key. Sharding allows for parallel processing of stream events and improved scalability.

  4. How do you manage the lifecycle of DynamoDB Streams?

    • Answer: You enable streams on a table, and DynamoDB automatically manages their creation. You can disable or delete streams as needed. Be aware of retention periods – data in the stream expires after a configurable time.

  5. What are the limitations of DynamoDB Streams?

    • Answer: Limitations include a maximum retention period (currently 24 hours for `NEW_IMAGE` and 7 days for `NEW_AND_OLD_IMAGES`), limits on the number of streams per table, and the potential for throughput limitations if processing events quickly becomes necessary.

  6. How can you consume DynamoDB Streams using Lambda?

    • Answer: You configure a Lambda function as a trigger for your DynamoDB stream. Whenever changes occur in the stream, Lambda automatically invokes the function, passing the stream record as input. This is a common and efficient way to process stream events.

  7. Describe how to use DynamoDB Streams with Kinesis Data Firehose.

    • Answer: Configure Kinesis Data Firehose as a consumer of the DynamoDB stream. Firehose will retrieve the stream records and load them into a destination like S3 or other data warehouse.

  8. How do you handle backpressure when consuming DynamoDB Streams?

    • Answer: Techniques for handling backpressure include increasing the number of consumers (e.g., multiple Lambda functions), implementing buffering (using SQS as a buffer), and adjusting the Lambda function's concurrency settings.

  9. What are the best practices for designing DynamoDB tables to work effectively with Streams?

    • Answer: Design tables with efficient partitioning keys to distribute writes across shards. Carefully consider the choice of `NEW_IMAGE` or `NEW_AND_OLD_IMAGES` based on your application's needs. Monitor stream consumption and adjust scaling as necessary.

  10. Explain the concept of sequence numbers in DynamoDB Streams.

    • Answer: Sequence numbers provide a unique identifier for each record in a stream. They are used to maintain the order of events and to resume processing from a specific point if necessary.

  11. How do you handle idempotency when processing DynamoDB Stream records?

    • Answer: Implement idempotency by using a unique identifier for each processed record (often combining the sequence number and primary key) and checking if the operation has already been performed. This prevents duplicate processing if a record is processed multiple times due to errors or retries.

  12. What are the cost implications of using DynamoDB Streams?

    • Answer: Costs are associated with storing data in the stream (based on retention period) and the number of consumed stream records. The cost increases linearly with the volume of data written to your DynamoDB table and your consumption rate.

  13. How do you monitor the health and performance of DynamoDB Streams?

    • Answer: Utilize CloudWatch metrics to track shard consumption rates, latency, and errors. Monitor the stream's storage usage and ensure sufficient throughput capacity. Properly designed alerts can notify you of potential issues.

  14. Explain how to use DynamoDB Streams for auditing purposes.

    • Answer: Consume the stream records and log them to a separate audit trail. Store the old and new image data to understand the changes that occurred. This provides a complete history of data modifications within your DynamoDB tables.

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