I want to avoid cold starts, so I’m running a Node.js Lambda function with Provisioned Concurrency turned on. Still, I see latency spikes (400–700 ms) in the logs that look exactly like cold starts.
The concurrency setting is higher than my peak traffic, so in theory, every time it runs, it should be “warm.”
What could be causing it:
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The latest version of the function does not have provisioned concurrency applied to it.
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Provisioned concurrency is lower than sudden burst load.
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Lambda is growing faster than the provisioned pool that was set aside for it.
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The internal Lambda infrastructure sometimes refreshes containers
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Using large dependency bundles or slow initialization code
Has anyone ever seen this “warm but not really warm” behavior?
Do you have any advice on how to fix or speed up
Lambda cold starts, even when provisioned concurrency is on?