When using Azure Functions in a consumption plan, what are best practices for cold-start mitigation, and how does that differ across regions?

Hi Suheb,

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Cold start is a key consideration for serverless architectures. For more information, see Cold starts. If cold start is a concern for your scenario, you can find a deeper dive in the post Understanding serverless cold start.

Premium plan is the recommended plan for reducing colds starts while maintaining dynamic scale. You can use the following guidance to reduce cold starts and improve availability in all three hosting plans. check here Azure Functions best practices | Microsoft Learn

 Consumption plan

• Review your use of Singleton patterns and the concurrency settings for bindings and triggers to avoid artificially placing limits on how your function app scales.
• Review the functionAppScaleLimit setting, which can limit scale-out
• Check for a Daily Usage Quota (GB-Sec) limit set during development and testing. Consider removing this limit in production environments.

The best practices to mitigate cold starts in this plan include:

• Minimizing initialization time by optimizing function code, such as avoiding large initialization logic, lazy loading dependencies, and preferring compiled languages like C# over interpreted ones like JavaScript.
• Programmatically keeping functions warm by scheduling periodic HTTP requests or pings to the function to prevent it from going idle, for example using an external cron job service.
• Considering migrating to newer plans like the Flex Consumption plan, which supports always ready instances for faster startup and per-function scaling, or the Premium plan that offers prewarmed instances and eliminates cold starts by design, though at a higher cost.
• Upgrade to a Flex, Premium or Dedicated Plan: The most straightforward solution to avoid cold starts is to upgrade from the Consumption plan to either the Flex Consumption, Premium or Dedicated (App Service) plan. These plans keep your functions warm and ready to execute at all times, effectively eliminating cold starts. Azure Functions scale and hosting | Microsoft Learn
• Monitoring function performance and cold start times with Application Insights and Azure Monitor to identify bottlenecks and further optimize.

Cold start latency can vary slightly across regions like the US, Europe, and Asia due to differences in infrastructure maturity, data center density, and network latency, but the mitigation strategies remain consistent globally. By selecting an optimal region close to your users, choosing the right hosting plan, and optimizing function design, you can achieve consistently fast startup and overall performance regardless of deployment region.

Refer document to improve cold start in Azure Functions: https://techcommunity.microsoft.com/blog/appsonazureblog/our-latest-work-to-improve-azure-functions-cold-starts/4164500

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