For events, keep in mind that pinging your lambda function with scheduled events will probably only keep one container warm, so if multiple requests are made to the function in parallel by users then some requests may still incur a cold start. If you want to keep more containers warm, you can invoke a separate lambda function on a schedule which concurrently makes multiple requests to your service. Answer from ScholarAncient on reddit.com
Reddit
reddit.com › r/aws › aws lambda provisioned concurrency vs keeping a lambda warm with events?
r/aws on Reddit: AWS Lambda provisioned concurrency vs keeping a lambda warm with events?
May 20, 2021 -
What are the pros/cons of each? I'm looking at reducing cold start for my app that end user is sensitive to the cold start effect and I will have sporadic/random requests coming in which is unpredictable. I can tolerate a very small amount of cold starts but not often.
I've looked at provisioned concurrency but it seems quite expensive. Why shouldn't I just use a lambda warmer and ping my lambda every 5 minutes to keep it warm? From my understanding the lambda warmer should be good enough but I have not tested it yet but it seems like a less costly approach.
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For events, keep in mind that pinging your lambda function with scheduled events will probably only keep one container warm, so if multiple requests are made to the function in parallel by users then some requests may still incur a cold start. If you want to keep more containers warm, you can invoke a separate lambda function on a schedule which concurrently makes multiple requests to your service.
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I would say it is generally not a good idea to artificially keep a Lambda "warm" one of the primary points of the services is that it scales. Why keep a Lambda running if there is no demand for it, that said I have seen unique cases where provisioned concurrency is required. Provisioned concurrency only really works if you can accurately estimate your concurrency and if your concurrency is fairly consistent. If you know your concurrency is going to be 10 and you have 10 provisioned instance then you greatly reduce (but not eliminate) the chance of cold boots However if the concurrency varies a lot then you are going to face cold boots when new instances are created. If cold boots are causing a problem the look at reducing the boot time by using a different language or reducing dependencies. Alternatively if you always need a container running look at other services. Finally and this might sound stupid but for concurrency don't forget the relationship with "duration"... I had to deal with people who estimated concurrency based on requests per second but their Lambda took 3 seconds to complete.
Qloudx
qloudx.com › no-more-lambda-warmups-use-provisioned-concurrency-instead
No More Lambda Warmups! Use Provisioned Concurrency Instead! – QloudX
You probably have an entirely separate function whose sole purpose is to get called by a CloudWatch Events schedule & invoke all other Lambdas in your fleet to warm them up. With Provisioned Concurrency, you need neither the function nor the CloudWatch Events schedule. It also takes away the ...
Videos
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AWS Lambda Provisioned Concurrency | Lambda Scaling and Concurrency ...
17:51
How does AWS Lambda Concurrency Work? - YouTube
13:02
AWS Lambda Concurrency - Provisional & Reserved - YouTube
13:09
AWS Lambda Concurrency Explained - YouTube
02:33
AWS Lambda Concurrency Explained | Reserved vs Provisioned ...
Medium
mark-sailes.medium.com › lambda-concurrency-and-why-you-dont-need-a-warmer-d9da6e205782
AWS Lambda concurrency and why you don’t need a warmer | by Mark Sailes | Medium
April 11, 2021 - It’s the Lambda service’s responsibility to make sure that each invocation of your function is executed as fast as possible. If all the current instances are busy with work, then the Lambda service will instruct a new microVM to start up, copy your code to it and get it ready to handle the waiting request. This process of provisioning a new microVM is called a cold start.
Amazon Web Services
docs.aws.amazon.com › aws lambda › developer guide › understanding lambda function scaling › configuring provisioned concurrency for a function
Configuring provisioned concurrency for a function - AWS Lambda
If you're using provisioned concurrency, consider restructuring your function code to optimize for low latency. For functions using provisioned concurrency, Lambda runs any initialization code, such as loading libraries and instantiating clients, during allocation time.
DEV Community
dev.to › aws-builders › provisioned-concurrency-reduce-cold-starts-in-aws-lambda-functions-part-1-4mob
Provisioned Concurrency - Reduce Cold Starts in AWS Lambda Functions Part 1 - DEV Community
March 13, 2024 - In such cases, it may be worth considering the possibility of having a running container. If our product requires predictable start times and latency, provisioned concurrency is the way to go.
Medium
aws.plainenglish.io › what-is-provisioned-concurrency-and-when-should-you-use-it-6eab44e9cd46
What is Provisioned Concurrency- and When Should You Use It? | by Joseph Schambach | AWS in Plain English
June 2, 2025 - What is Provisioned Concurrency- and When Should You Use It? Reduce cold start latency in Lambda functions. TL;DR: Provisioned Concurrency keeps your AWS Lambda functions “warm,” eliminating cold …
Pulumi
pulumi.com › home › blog › provisioned concurrency: avoiding cold starts in aws lambda
Provisioned Concurrency: Avoiding Cold Starts in AWS Lambda | Pulumi Blog
March 19, 2025 - A trick known as Lambda Warmers uses kept-alive workers to reduce the frequency of cold starts. The idea is to have a CloudWatch timer that fires every few minutes and sends N parallel requests to the target Lambda. If all those requests land at the same time, AWS has to provision at least N workers to process them.
Medium
hardiks.medium.com › is-provisioned-concurrency-better-than-aws-lambda-8e17e714e13e
Is Provisioned Concurrency better than AWS Lambda | by Hardik Shah | Medium
November 3, 2022 - Provisioned concurrency: A dynamic number of concurrent requests that scales up and down based on usage, costs, and other factors (such as the amount of time it takes to run a function). Dedicated Instance on Demand (Dedicated Instances or Spot instances) ... The first option is an instance that you can launch if you want to use AWS Lambda in real time mode.
Quintagroup
quintagroup.com › blog › aws-lambda-provisioned-concurrency
AWS Lambda: Why Provisioned Concurrency is better than On-Demand Lambda — Quintagroup
June 1, 2023 - Provisioned Concurrency is a new feature of AWS Lambda in Serverless. What does it do? It minimizes the estimate of cold starts by generating execution environments ahead of usage completely up to running the initialization code.
Substack
hieudd.substack.com › p › warmup-solves-98-of-aws-lambda-cold
Warmup solves 98% of AWS Lambda cold starts while 100x cheaper than provisioned concurrency
November 13, 2023 - Warmup is able to keep concurrent execution at 10 most of the time, and warmup latency is <100ms for 10 concurrency invocations. Warmup cost estimations are 100x cheaper than provisioned concurrency at same level of concurrency.
LinkedIn
linkedin.com › pulse › simplifying-aws-lambda-understanding-reserved-vs-piñero-estrada-davme
Simplifying AWS Lambda. Understanding Reserved vs. Provisioned Concurrency
April 5, 2024 - Reserved Concurrency is about guaranteeing availability, while Provisioned Concurrency, with its “pre-warm” mode, is about ensuring immediate, predictable performance, eliminating cold start latency.
Reddit
reddit.com › r/aws › lambda provisioned concurrency
r/aws on Reddit: Lambda provisioned concurrency
July 3, 2023 -
Hey, I'm a huge serverless user, I've built several applications on top of Lambda, Dynamo, S3, EFS, SQS, etc.
But I have never understood why would someone use Provisioned Concurrency, do you know a real use case for this feature?
I mean, if your application is suffering due to cold starts, you can just use the old-school EventBridge ping option and it costs 0, or if you have a critical latency requirement you can just go to Fargate instead of paying for provisioned concurrency, am I wrong?
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pings won't save you from cold starts. if the workload just crosses what the current capacity can handle, a new instance will be warmed up. you have no control over whether it will be a ping or an actual user. pinging works as long as one single instance can serve all demands. fargate requires 24/7 running tasks, because the startup times are even worse than lambda's. if you want 24/7 running tasks together with scaling and all, sure, do that, but it requires a whole lot more setup.
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I mean, if your application is suffering due to cold starts, you can just use the old-school EventBridge ping option and it costs 0 This isn't nearly as effective as there's no real way to make EventBridge keep 100 or 1000 or more environments warm. If you have a very low traffic application maybe this method still makes sense, but for anything else PC is going to be more reliable
Ran The Builder
ranthebuilder.cloud › post › optimize-aws-lambda-with-dynamic-provisioned-concurrency
Optimize AWS Lambda with Dynamic Provisioned Concurrency
July 8, 2024 - Provisioned concurrency ensures that multiple Lambda functions remain ‘warm’, meaning they are initialized and prepared to respond promptly, unlike on-demand Lambda, which initializes resources upon invocation. Pre-initializing an environment includes tasks such as code download, environment setup, and running initialization code.
How-To Geek
howtogeek.com › home › cloud › should you use provisioned concurrency for aws lambda functions?
Should You Use Provisioned Concurrency for AWS Lambda Functions?
July 7, 2023 - Compared to the prior example, where functions are started cold, provisioned concurrency starts them all in advance and keeps them warm. When an invocation is needed, Lambda will use the warm functions to execute it.
Awsbites
awsbites.com › 129-lambda-provisioned-concurrency
Lambda Provisioned Concurrency
In this episode, we discuss AWS Lambda provisioned concurrency. We start with a recap of Lambda cold starts and the different concurrency control options. We then explain how provisioned concurrency works to initialize execution environments in advance to avoid cold starts.
AWS re:Post
repost.aws › questions › QUoK1sk8CUTyGN7VESAcjlgA › why-cold-starts-of-a-lambda-with-provisioned-concurrency-are-much-slower-than-cold-starts-of-on-demand-instances
Why cold starts of a lambda with provisioned concurrency are much slower than cold starts of on demand instances? | AWS re:Post
July 30, 2023 - I think you do not get the boost during Provisioned Concurrency initialization. You can prove this by increasing your function's memory to 1.7GB. In this case you will get approximately the same amount of CPU as the boost you get. ... Thank you for confirming. Tested and with more CPU On-Demand instances are still a bit faster but the difference is not that visible (10-20%) ... Hi, If you look at the diagrams of https://aws.amazon.com/blogs/compute/operating-lambda-performance-optimization-part-1/, you will notice that the so-called "Execution Initialization Code" in the post happens as part of lambda execution itself in a cold start while it happens as part of initialization phase with provisioned concurrency.
No Dogma Blog
nodogmablog.bryanhogan.net › 2022 › 11 › keeping-your-net-lambda-function-warm-with-provisioned-concurrency
Keeping your .NET Lambda Function Warm with Provisioned Concurrency | no dogma blog
November 4, 2022 - Cold starts with .NET AWS Lambda functions are a concern for some, but provisioned concurrency provides a simple and cost-effective way to keep your Lambda function warm.
Hacker News
news.ycombinator.com › item
Provisioned concurrency is insanely expensive. If you have any kind of a thunder... | Hacker News
October 13, 2021 - I'm sure it has some use-cases in some kind of backoffice task queue scenario, but Lambda is nearly unusable in a web context unless you have a very trivial amount of traffic · Taking all of this into account, Lambda is then useful for a very small niche:
Stack Overflow
stackoverflow.com › beta › discussions › 78231813 › difference-between-aws-lambda-reserved-and-unreserved-concurrency
Difference between AWS Lambda Reserved and Unreserved Concurrency - Stack Overflow
Whenever a lambda function is triggered, a runtime of the function is executed along with its dependencies which processes your request. So there is always a slight delay also known as latency when a new runtime is prepared. To solve this problem you assign a provisioned concurrency that keeps the desired number of lambda runtimes always ready to process the request which results in faster responses as there is no cold start.