Retrieving the N most recent entries from DynamoDB through Lambda Function

Question

Retrieving the N most recent entries from DynamoDB through Lambda Function

Within my DDB table, I have records containing a field called Timestamp that holds date and time string values like: 2023-11-14T01:22:53.945Z

My goal is simply to perform a database query that retrieves N entries sorted in descending order based on this timestamp. I've come across discussions regarding GSI, ranges, and sort keys which feel overwhelming and confusing.

I don't have specific code examples to share, as I've experimented with different approaches found on ChatGPT and Stack Overflow posts but haven't been able to determine the correct method, especially considering some suggest using Timestamp as secondary keys or defining them within GSI's. (using JavaScript)

javascript amazon-web-services aws-lambda amazon-dynamodb dynamodb-queries

Answer 1

Answer №1

For scenarios where you require maintaining order in DynamoDB, a GSI is necessary. In this case, the timestamp should be chosen as the sort key to ensure proper ordering. The question then becomes, what should serve as the partition key?

If your table's overall throughput does not exceed 1000 WCU, a simple solution is to use a static value for the partition key of your GSI:

GSIPK	Timestamp	data
1	2023-11-20T20:00:000Z	some data
1	2023-11-20T21:00:000Z	some data
1	2023-11-20T22:00:000Z	some data
..	..	..
1	2023-11-29T16:00:000Z	some data

This data model allows for retrieving the latest or oldest N records using the Query command. The SQL equivalent would look like the following:

SELECT * 
FROM my-table.my-index 
WHERE GSIPK = 1 
LIMIT 10

If your table requires more than 1000 WCU, using a static key may lead to a hot partition on your index. In such cases, sharding your GSI is necessary, which involves using a random (known) character as the GSIpk and may result in making multiple requests.

Answer 2

For scenarios where you require maintaining order in DynamoDB, a GSI is necessary. In this case, the timestamp should be chosen as the sort key to ensure proper ordering. The question then becomes, what should serve as the partition key?

If your table's overall throughput does not exceed 1000 WCU, a simple solution is to use a static value for the partition key of your GSI:

GSIPK	Timestamp	data
1	2023-11-20T20:00:000Z	some data
1	2023-11-20T21:00:000Z	some data
1	2023-11-20T22:00:000Z	some data
..	..	..
1	2023-11-29T16:00:000Z	some data

This data model allows for retrieving the latest or oldest N records using the Query command. The SQL equivalent would look like the following:

SELECT * 
FROM my-table.my-index 
WHERE GSIPK = 1 
LIMIT 10

If your table requires more than 1000 WCU, using a static key may lead to a hot partition on your index. In such cases, sharding your GSI is necessary, which involves using a random (known) character as the GSIpk and may result in making multiple requests.

Retrieving the N most recent entries from DynamoDB through Lambda Function

Answer №1

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