How to find all lambdas with provisioned concurrency in AWS

Alternative Text
by Dmitry Elisov
Oqtacore CTO

AWS lambdas are great for many various use cases. They are cheap (if used correctly), fast and easy to maintain. A lambda once written can easily be launched again, unlike most other code that you have on your local disk.

But there are some downfalls in lambdas – one is that they need some warm-up time if they are not used often. By default, your lambda code is not loaded into the memory of the worker that runs this lambda. And when an unused lambda is invoked, it first needs to be loaded into a container and started. Such a situation is called a cold start, and a cold start takes 700ms to 3 seconds from our experience.

After a cold start, a container stays warm for about 30-40 minutes, and then a cold start will happen again.

The function lifecycle logo

Source: AWS 

But what if you need your lambda to be used rarely, but each response should be very quick? For example, it might be your newly developed startup project with a marketplace page for which some lambda processes user requests. Until you get enough users to keep your lambdas always warm, you might need to keep them warm yourself so that users do not experience multi-second load times while accessing the marketplace. Otherwise, your conversion rates will be a disaster.

lambda processes

Source: Cloudflare  

And AWS thought of that – they allow you to keep your lambdas warm. It is called provisioned concurrency (do not mistake it with reserved concurrency which is absolutely different).

Provisioned concurrency keeps containers with your lambda warm, and it will take just a few tens of milliseconds to start the lambda.

However, take note: the provisioned concurrency is not free. And oftentimes you just forget which lambdas have it enabled, and checking each lambda can take 30 seconds even if you know where to check – that’s because provisioned concurrency settings are just buried too deep in the lambda settings and also require checking each version of lambda separately… Extremely bad UX.

So when we at OQTACORE faced an issue of needing to check where we have provisioned concurrency enabled, there was no better way than to write a simple lambda to fight provisioned concurrency of other lambdas 🙂

Here is the code:

const AWS = require(‘aws-sdk’);

const lambda = new AWS.Lambda();

exports.handler = async (event) => {

let promises = [];

const allLambdas = await getAllLambdas();

const resultArr = [];

for (let i = 0; i < allLambdas.length; i++) {

     promises.push(checkConfig(allLambdas[i].FunctionName, resultArr));


await Promise.all(promises);

return resultArr;


async function getAllLambdas() {

let nextMarker;

let allLambdas = [];

do {

     var params = {

         Marker: nextMarker,

         MaxItems: 10


     let result = await lambda.listFunctions(params).promise();

     allLambdas = […allLambdas, …result.Functions];

     nextMarker = result.NextMarker;

} while (nextMarker != null);

return allLambdas;


async function checkConfig(funcName, resultArr) {

let retries = 5; //sometimes listProvisionedConcurrencyConfigs() crashes

while (retries– > 0) {

     try {

         var params = {

             FunctionName: funcName


         const conf = await lambda.listProvisionedConcurrencyConfigs(params).promise();

         if (conf.ProvisionedConcurrencyConfigs.length > 0) {





     catch (ex) {






This code will return you an array of lambdas that have provisioned concurrency enabled. Please note that this works only in the same region of the lambda! You can modify the code yourself to process all regions that you need, or just deploy this code in every region where you have lambdas.

If you are looking for software developers who know cloud and blockchain, make sure to check OQTACORE


Frequently Asked Questions:
How do I start working with OQTACORE?

We have a call and discuss details of the project

You make an initial payment for the project

Our CTO and your assigned Project Manager write the specification documents for the project

We discuss and approve the specs with you

We compile the specs into a development schedule

We implement the specs with releases every two weeks

How much does MVP cost?

It depends on the package you choose. Feel free to explore each package with prices and examples on our landing page or use our calculator.

How much time is take to build an MVP?

Prototype – 10 days

MVP for one platform (Android/iOS/Web) – 1-3 months

MVP for three platform (Android/iOS/Web) – 3-6 months

Do you sign an NDA?

We sign an NDA with each customer. All the source code and intellectual property will belong to you.

Who will I communicate with during the project?

You will have 24/7 access to PM Saveliy Leniivin and CTO Dmitry Elisov, who will guide your project from start to finish.

What are the team’s working hours?

We work on weekdays Pacific Standard Time (PST), UTC -8. 8am – 11pm. This schedule allows us to communicate with you and to do the work as efficiently as possible, regardless of the time zone difference.

How can I control the project?

You will have access to Jira (it is a project management software used by many companies in the world), where we will manage your entire project. There, you will see each task and its due date.

Is it possible to add/remove features after the project has started and specification and implementation plan have been approved?

Yes, it is possible. We will create an additional specification, in which we will write down the additional features you want to introduce, and we will add them to the UI design and development plan.

What will I get as the end result?

A ready-to-use application that can be downloaded from the App Store, Google Play or used as a web app + all copyright for the code + documentation.

Can I come and visit your office?

You can visit us any time!

Are you a team of just 7?

Our core MVP team consists of seven people: CTO, IT PM, Designer, Backend software developer, Frontend software developer, QA tester. This is an example of our team that will interact with you during the creation of your MVP. As the app develops and expands, other members will join the team.

Apart from developing MVPs from scratch, we have a team that is engaged in maintaining current projects and scaling them. For one of our customers, we have assembled and manage a team of 23 programmers who are continuing to develop our customer’s successful startup right now.

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