Stream vs polling comparison in DynamoDB

Introduction

Streams and polling are two ways to get updates from a database. Streams send changes as they happen, while polling checks for changes regularly.

You want to react immediately when data changes, like updating a live dashboard.

You need to process changes in order, such as syncing data between systems.

You want to reduce unnecessary checks to save resources and cost.

You have a simple app that can check for updates every few seconds without delay.

You want to keep your system simple and avoid managing stream processing.

Syntax

DynamoDB

Stream: Enable DynamoDB Streams on your table and use AWS Lambda or Kinesis to process changes.

Polling: Write code to query the table at intervals using Scan or Query operations.

Streams provide real-time change data capture.

Polling requires setting a time interval and may miss immediate changes.

Examples

This query fetches new or updated items since the last check.

DynamoDB

-- Polling example: Query table every 10 seconds
SELECT * FROM MyTable WHERE UpdatedAt > last_checked_time;

Lambda automatically runs when data changes, no need to query manually.

DynamoDB

// Stream example: Lambda function triggered by DynamoDB Stream
// Process each record as it arrives

Sample Program

This query fetches orders placed after June 1, 2024. You would run this repeatedly to check for new orders.

DynamoDB

-- Polling example: Get new items added after a timestamp
SELECT * FROM Orders WHERE OrderDate > '2024-06-01T00:00:00Z';

Important Notes

Streams are better for real-time and ordered processing.

Polling can cause delays and extra cost if done too frequently.

Use streams when you want to react instantly without writing polling code.

Summary

Streams push changes to you immediately.

Polling asks for changes at set times.

Choose streams for real-time needs, polling for simple or less time-sensitive tasks.