Understanding AWS Lambda Concurrency: Reserved vs. Provisioned

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. We cover how to enable it, pricing details, common issues like over/under-provisioning, and alternatives like self-warming functions or using other services like ECS and Fargate.

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In this episode, we mentioned the following resources:

• Episode 60: "What is AWS Lambda": https://awsbites.com/60-what-is-aws-lambda/
• Episode 104: "Explaining AWS Lambda Runtimes": https://awsbites.com/104-explaining-lambda-runtimes/
• Episode 108: "Solving Lambda Cold Starts in Python": https://awsbites.com/108-how-to-solve-lambda-python-cold-starts/
• Episode 120: "Lambda Best Practices": https://awsbites.com/120-lambda-best-practices/
• AWS Lambda Concurrency Explained by James Eastham: https://www.youtube.com/watch?v=KHACnNKTefI
• Provisioned Concurrency pricing: https://aws.amazon.com/lambda/pricing/#Provisioned_Concurrency_Pricing
• Less than 1% of invocations are cold-starts (statement): https://docs.aws.amazon.com/lambda/latest/operatorguide/execution-environments.html
• Middy Warmup Middleware: https://middy.js.org/docs/middlewares/warmup/
• Lambda speculative warm-up init (mention in the Docs): https://docs.aws.amazon.com/lambda/latest/dg/lambda-runtime-environment.html#:~:text=For%20functions%20using,on%20this%20behavior.
• Episode 64: "How do you write Lambda Functions in Rust": https://awsbites.com/64-how-do-you-write-lambda-functions-in-rust
• Episode 128: "Writing a book about Rust and Lambda": https://awsbites.com/128-writing-a-book-about-rust-and-lambda/

Do you have any AWS questions you would like us to address?

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