In-depth .NET Azure Functions: Flex plan, Isolated mode and performance

Is the new Azure Functions Flex plan always better? Discover the hidden networking trade-offs that can break your app at scale.

#1about 5 minutes

Introducing the new Flex Consumption plan for Azure Functions

The new Flex Consumption plan, built on Kubernetes, replaces the old in-process model with an isolated worker model for better performance and portability.

#2about 6 minutes

Flex plan features, limits, and VNet challenges

The Flex plan includes "always ready" instances and free VNet integration, but is constrained by subscription-level vCore limits and potential IP exhaustion at scale.

#3about 7 minutes

Load testing Flex vs classic Consumption plans

Load tests reveal that the Flex plan scales significantly faster for sudden traffic spikes compared to the classic Consumption plan, which is better for steady workloads.

#4about 2 minutes

Optimizing Flex plan instance size for performance

Choosing the right instance size is key, with 0.5GB instances offering the fastest scaling for spikes and larger instances providing better cost-efficiency.

#5about 5 minutes

Advanced performance tuning with AOT and dependencies

While Native AOT offers limited benefits, you can significantly improve performance by minimizing .NET dependencies and configuring concurrency settings in host.json.

#6about 3 minutes

Portability and final recommendations for migration

The isolated worker model simplifies containerizing functions for migration, and it's crucial to load test, monitor SDK updates, and prepare for Flex to become the default.