Always Ready Instance Count for Flex-Consumption Plan.

Question

Always Ready Instance Count for Flex-Consumption Plan.

Amal Syed 60

I am running Flex Consumption Plan for my Function App (Non-Prod - No Zone Redundancy) which consists of 7 HTTP based triggers and 2 Queue based triggers. I have configured "Always Ready" for my HTTP triggers as shown below
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However, when I check the Metric "Always Ready Units" in App Insights , I see the count spiking between 5-6 like below.

User's image

Does this mean, I have 5-6 Always ready units running & will I be billed for all of them? I am having hard time understanding this.

Also is there a way by which we can configure Always Ready for Queue based trigger functions?

Amal Syed 60 Reputation points

2025-10-24T12:38:05.37+00:00

Thanks for explanation.
In this case, what significance does the count 1 which we configure have?
Anonymous

2025-10-25T09:29:02.5366667+00:00

Hi Amal Syed, thanks for follow-up

When you configure the Always Ready instance count to 1 in the Flex Consumption plan, Azure Functions maintains one pre-warmed instance of the function app for the specified HTTP trigger.

This instance remains initialized and ready to process incoming requests without delay, reducing cold start latency. Each Always Ready configuration represents a dedicated pre-initialized instance that ensures consistent and responsive function execution.

I hope this clarifies the behavior of the Always Ready setting, feel free to reach out if you need further assistance or additional details.
Amal Syed 60 Reputation points

2025-10-27T04:02:48.4866667+00:00

Thank you. But can you explain, how "Always Ready" instance count is then 5-6? (Low or Zero traffic mostly) even when I configured 1 instance under HTTP Trigger?
Anonymous

2025-10-27T17:58:06.4666667+00:00
Hey Hi Amal Syed, thanks for follow-up

When you configure Always Ready instance count to 1 in the Flex Consumption plan, Azure keeps a minimum of one pre-warmed HTTP-triggered function instance ready to reduce cold starts.

However, the Always Ready Units metric can show spikes to 5-6 due to Azure proactively scaling additional pre-warmed instances for load balancing, health checks, infrastructure updates, or anticipated traffic beyond the configured minimum this dynamic scaling optimizes responsiveness and availability even during low traffic periods. You are billed for all active Always Ready instances, not just the configured count.

I hope this helps do let me know if you have any questions
Anonymous

2025-10-29T06:34:16.5633333+00:00

Hi Amal Syed, following up to see if my response addressed your issue and helped, do let me know if you have any further questions on this.
Anonymous

2025-10-31T02:54:05.12+00:00

Hello Amal Syed, checking to see if my response addressed your issue and helped, do let me know if you have any further questions on this.

1 answer

Your answer

Amal Syed 60 Reputation points

2025-10-24T12:38:05.37+00:00

Thanks for explanation.
In this case, what significance does the count 1 which we configure have?
Anonymous

2025-10-25T09:29:02.5366667+00:00

Hi Amal Syed, thanks for follow-up

When you configure the Always Ready instance count to 1 in the Flex Consumption plan, Azure Functions maintains one pre-warmed instance of the function app for the specified HTTP trigger.

This instance remains initialized and ready to process incoming requests without delay, reducing cold start latency. Each Always Ready configuration represents a dedicated pre-initialized instance that ensures consistent and responsive function execution.

I hope this clarifies the behavior of the Always Ready setting, feel free to reach out if you need further assistance or additional details.
Amal Syed 60 Reputation points

2025-10-27T04:02:48.4866667+00:00

Thank you. But can you explain, how "Always Ready" instance count is then 5-6? (Low or Zero traffic mostly) even when I configured 1 instance under HTTP Trigger?
Anonymous

2025-10-27T17:58:06.4666667+00:00

Hey Hi Amal Syed, thanks for follow-up

When you configure Always Ready instance count to 1 in the Flex Consumption plan, Azure keeps a minimum of one pre-warmed HTTP-triggered function instance ready to reduce cold starts.

However, the Always Ready Units metric can show spikes to 5-6 due to Azure proactively scaling additional pre-warmed instances for load balancing, health checks, infrastructure updates, or anticipated traffic beyond the configured minimum this dynamic scaling optimizes responsiveness and availability even during low traffic periods. You are billed for all active Always Ready instances, not just the configured count.

I hope this helps do let me know if you have any questions
Anonymous

2025-10-29T06:34:16.5633333+00:00

Hi Amal Syed, following up to see if my response addressed your issue and helped, do let me know if you have any further questions on this.
Anonymous

2025-10-31T02:54:05.12+00:00

Hello Amal Syed, checking to see if my response addressed your issue and helped, do let me know if you have any further questions on this.

Answer 1

Hi Amal Syed,

Thanks for posting your question in Microsoft Q&A forum

In a Flex Consumption Plan for Azure Functions, when you enable the Always Ready feature for HTTP triggers, it ensures that the function app is always ready to handle incoming HTTP requests without a cold start delay. This means that a certain number of instances will remain always ready and running, which helps to reduce response times.

Based on the images you provided, it looks like your Always Ready Units metric is showing a count that spikes between 5-6. This suggests that, at certain times, 5-6 instances are being kept always ready to handle HTTP requests. These spikes represent the number of Always Ready instances at any given time.

1.Always Ready Units Spiking: When you see a spike in the Always Ready Units metric between 5-6, it indicates that you have that many Always Ready instances running. Yes, you will be billed for all of them as they are actively allocated for your app. The purpose of this is to reduce cold start times for your HTTP-triggered functions, ensuring they're ready to handle incoming requests more quickly. The total number of executions. In always ready billing, there are no free grants.

The minimum billable execution period for both execution modes is 1,000 ms. Past that, the billable activity period is rounded up to the nearest 100 ms. You can find details on the Flex Consumption plan billing meters in the Monitoring reference.

For details about how costs are calculated when you run in a Flex Consumption plan, including examples, see Consumption-based costs.

You can refer to Azure's pricing documentation for detailed costs related to Always Ready instances in a Flex consumption plan

2.Queue-based Trigger Functions: Currently, the Always Ready configuration is specifically available for HTTP and other specific trigger types like Durable and Blob triggers. Unfortunately, as of now, there isn't a way to configure Always Ready for Queue-based functions via the Azure portal or Azure CLI.

Refer document: Azure Functions Flex Consumption plan hosting | Microsoft Learn

I hope the provided answer is helpful, do let me know if you have any further questions on this Please accept as Yes if the answer is helpful so that it can help others in the community.

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Always Ready Instance Count for Flex-Consumption Plan.

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