DynamoDB AutoScaling still throttles

Question

I have an application using DynamoDB and I noticed they just implemented autoscaling which is awesome. I love the concept and the timing for my app is pretty perfect. However I am still getting some issues that I wonder if I can't tweak settings to remove.

My application gets definite spikes in usage so I think this is an ideal thing to use, however with autoscaling on I still am getting some throttling. Here is my read graphs for the last 12 hours:

As you can see, when it spikes the usage is set low, so it throttles for a minute or two until the update kicks in, then works. That's ok I guess and better than not scaling, but I would like it not to throttle at all...

Is there any way to tell DynamoDB to never throttle unless it goes over 100 (or 200 or whatever I set as the top limit)? Just if it gets a surge turn up the throughput for 15 minutes or whatever until the surge is over?

Answer 1

Autoscaling uses CloudWatch. You can see these alarms by going to the CloudWatch dashboard and look for the alarms that include your table name and "DO NOT EDIT OR DELETE" in the description.

Why am I telling you this?

Well, the CloudWatch has some minimal period granularity. Currently it's 1 minute. It means that it will wait at least for 1 minute before firing any event to its listeners. Therefore, it will take at least one minute after the load starts until the capacity is increased. Actually it will be even more, since increasing the capacity also takes time. Bottom line: if you have very large spike, some requests may be throttled, since the the auto-scaling will not yet take effect and bursting can be exhausted.

The simple, but costly, solution will be increasing the initial capacity.

If you know about the upcoming spike in advance (e.g. you have some job running periodically, or customer peaks in certain times) you can use API to modify autoscaling programmatically.