As of 2024, eachEach AWS Lambda instance runs within a lightweight, isolated environment powered by [[Firecracker (software)|Firecracker]] microVMs. These microVMs are initialized with a runtime environment based on [[Amazon Linux]] (Amazon Linux AMI or Amazon Linux 2), a custom Linux distribution developed by AWS. Firecracker provides hardware-virtualization-based isolation, aiming to achieve near-bare-metal performance with minimal overhead. AWS claims that, unlike traditional virtual machines, these microVMs launch in milliseconds, enabling rapid and secure function execution with a minimal memory footprint. The Amazon Linux AMI is specifically optimized for cloud-native and serverless workloads, aiming to provide a lightweight, secure, and performant runtime environment. <ref>{{Cite book |title=Accelerating Server-Side Development with Fastify: A comprehensive guide to API development for building a scalable backend for your web apps |isbn=9781800568747}}</ref><ref>{{Cite web |title=Firecracker – Lightweight Virtualization for Serverless Computing |url=https://aws.amazon.com/blogs/aws/firecracker-lightweight-virtualization-for-serverless-computing/ }}</ref><ref>{{Cite web |title=Secure and fast microVMs for serverless computing |url=https://firecracker-microvm.github.io/ }}</ref>
{{As of Dec 2024|2025}}, AWS Lambda supports [[Node.js]], [[Python (programming language)|Python]], [[Java (programming language)|Java]], [[Go (programming language)|Go]], [[.NET]], [[Ruby (programming language)|Ruby]] and custom runtimes.<ref>{{Cite web |title=Lambda runtimes |url=https://docs.aws.amazon.com/lambda/latest/dg/lambda-runtimes.html }}</ref>
==Features==
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* Impeded local testing.
* No [[Tree shaking|tree-shaking]] optimizations.
AWS Serverless Hero Yan Cui recommends alternative code-sharing strategies using package managers (e.g., [[Npm|NPM]]) due to these constraints. <ref name=":1" />
