Avoid throttle dynamoDB

Question

I am new to cloud computing, but had a question if a mechanism as what I am about to describe exists or is possible to create?

Dynamodb has provisioned throughput (eg. 100 writes/second). Of course, in real world application real life throughput is very dynamic and will almost never be your provisioned amount of 100 writes/second. I was thinking what would be great would be some type of queue for dynamodb. For example, my dynamodb during peak hours may receive 500 write requests per second (5 times what I have allocated) and would return errors. Is it there some queue I can put in between the client and database, so the client requests go to the queue, the client gets acknowledged their request has been dealt with, then the queue spits out the request to the dynamodb at a rate of 100/ writes per second exactly, so that way there are no error returned and I don't need to raise the through put which will raise my costs?

Answer 1

One update for those seeing this recently, for having burst capacity DynamoDB launched on 2018 the On Demand capacity mode.

You don't need to decide on the capacity beforehand, it will scale read and write capacity following the demand.

See: https://aws.amazon.com/blogs/aws/amazon-dynamodb-on-demand-no-capacity-planning-and-pay-per-request-pricing/

Answer 2

Putting AWS SQS is front of DynamoDB would solve this problem for you, and is not an uncommon design pattern. SQS is already well suited to scale as big as it needs to, and ingest a large amount of messages with unpredictable flow patterns.

You could either put all the messages into SQS first, or use SQS as an overflow buffer when you exceed the design thoughput on your DynamoDB database.

One or more worker instances can than read messages from the SQS queue and put them into DynamoDB at exactly the the pace you decide.

If the order of the messages coming in is extremely important, Kinesis is another option for you to ingest the incoming messages and then insert them into DynamoDB, in the same order they arrived, at a pace you define.

IMO, SQS will be easier to work with, but Kineses will give you more flexibility if your needs are more complicated.

Answer 3

This cannot be accomplished using DynamoDB alone. DynamoDB is designed for uniform, scalable, predictable workloads. If you want to put a queue in front of DynamoDB you have do that yourself.

DynamoDB does have a little tolerance for burst capacity, but that is not for sustained use. You should read the best practices section Consider Workload Uniformity When Adjusting Provisioned Throughput, but here are a few, what I think are important, paragraphs with a few things emphasized by me:

For applications that are designed for use with uniform workloads, DynamoDB's partition allocation activity is not noticeable. A temporary non-uniformity in a workload can generally be absorbed by the bursting allowance, as described in Use Burst Capacity Sparingly. However, if your application must accommodate non-uniform workloads on a regular basis, you should design your table with DynamoDB's partitioning behavior in mind (see Understand Partition Behavior), and be mindful when increasing and decreasing provisioned throughput on that table.

If you reduce the amount of provisioned throughput for your table, DynamoDB will not decrease the number of partitions . Suppose that you created a table with a much larger amount of provisioned throughput than your application actually needed, and then decreased the provisioned throughput later. In this scenario, the provisioned throughput per partition would be less than it would have been if you had initially created the table with less throughput.

There are tools that help with auto-scaling DynamoDB, such as sebdah/dynamic-dynamodb which may be worth looking into.