DynamoDB read usage spike when using frontend API

This is very interesting situation! The fact that you see different DynamoDB read usage between Postman and your React App suggests that the difference is likely in how the requests are being made or handled, rather than anything intrinsic to DynamoDB itself.

Here are a few possible causes to consider:

1. Frequency of Requests: If your React App is making more requests per second than Postman, this could account for the increased read usage.

2. Parallelization of Requests: If your React App is making multiple requests in parallel, this could cause a spike in read usage. Postman typically sends requests one at a time.

3. Data Volume: If the React App is fetching more data (more items or larger items) than Postman, this would result in more read capacity unit usage. Remember, DynamoDB charges read capacity units based on item size, with one unit representing one read per second for items up to 4 KB.

4. Consistency: DynamoDB has two read types: eventually consistent and strongly consistent. Strongly consistent reads use twice the read capacity units as eventually consistent reads. Check if there's a difference in the consistency model between your Postman and React App requests.

To debug this, I would recommend you start by logging detailed request and response information in both Postman and your React App. Compare the logs to identify any differences in the frequency of requests, the size of the data being fetched, or the request parameters. AWS X-Ray can also be useful for tracing requests and identifying bottlenecks or differences in request handling.

Hope this helps !!