Throttling in Ondemand Dynamodb table


One of our dynamodb tables reads are getting throttled even though the table has On-demand capacity mode. I have got the possible reasons behind throttling -

But I am not able to find solution for this issue. What are the possible fixes I can try to avoid throttling ?

Reads Graph - Reads of the DDB table

Throttles Graph - Throttles of the table

GSI Reads - GSI Reads

GSI throttles - GSI Throttles

asked 5 months ago223 views
1 Answer

In on-demand mode read throttling occurs when you exceed twice your previous peak within 30 minutes, or you exceed your partition throughput limit of 3000 RCU per second.

While it may appear you are not exceeding the 3000 RCU, that is because CloudWatch works on a per-minute granularity, as thats the period DynamoDB emits metrics to CloudWatch. This means that you see a per min value, which is the average per second consumption within those 60 seconds.

The first step to overcoming a hot partition/key is to enable CloudWatch Contributor Insights, this will give you insight into which key(s) are causing the issue. From there you can understand if you can address the issue with some changes to your access patterns/code. If not then you may look into implementing a caching solution such as DAX which can offset your reads from the table to be served by DAX.

If you are using Strongly Consistent Reads, I would also suggest changing to Eventually Consistent Reads which can half your read throughput consumption.

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answered 5 months ago
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reviewed 5 months ago
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reviewed 5 months ago
  • We are using eventually Consistent Reads only. Added GSI Reads and throttles graph for reference

  • The issue, nor the suggested fixes do not change. Enable CCI, see what keys are hot and work out a fix in your access patterns. If thats not possible, use a cache in front such as DAX which is API compatible with DynamoDB.

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