Amazon Redshift concurrency scaling - How much time it takes to complete scaling and setting threshold to trigger it

Question

Hi Team,
I have an existing redshift cluster, where I want to enable concurrency scaling. I had few queries related to the same :
1. My cluster having 2 on demand ra3.4xlarge nodes is running since March 2021. AWS docs mentions that the running redshift cluster accrues 1 hour of free cluster usage credit every 24 hours which never expire. Does it mean that, my cluster would already have 18 months * 30 credit usage hours already accrued, since concurrency scaling was never enabled for this cluster.?
2. When the does the concurrency scaling feature kicks in ? Is it only when the queries starts getting queued up ? Can we define some kind of threshold like cpu %utilization or memory % utilization, which would automatically start the concurrency scaling process ?
3. How much time does it take for cluster to complete the autoscaling process and start serving queries ?
 
Thanks!

Accepted Answer

Hi There

1. Redshift clusters earn up to one hour of free Concurrency Scaling credits per day. Credits are earned on an hourly basis for each active cluster in your AWS account, and can be consumed by the same cluster only after credits are earned. **You can accumulate up to 30 hours of free Concurrency Scaling credits for each active cluster.** Credits do not expire as long as your cluster is not terminated.  [1]
2. Concurrency Scaling clusters are added when a WLM slots are taken by running queries and other queries are waiting for a WLM slot to execute.  You route queries to concurrency scaling clusters by enabling a workload manager (WLM) queue as a concurrency scaling queue. To turn on concurrency scaling for a queue, set the Concurrency Scaling mode value to auto. [2]
3. Amazon Redshift automatically adds query processing power in seconds to process queries without any delays. [3]

[1] https://aws.amazon.com/redshift/pricing/#Concurrency_Scaling_pricing

[2] https://docs.aws.amazon.com/redshift/latest/dg/concurrency-scaling.html

[3] https://aws.amazon.com/redshift/features/concurrency-scaling/

Amazon Redshift concurrency scaling - How much time it takes to complete scaling and setting threshold to trigger it

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