Performance on Fulgurion Systems Blog

Rust Meets Serverless, Part 3: Anatomy of a Cold Start

Wed, 22 Apr 2026 00:00:00 -0300

In Part 2 I measured the cold start of a minimal Rust Lambda at 18 to 22 ms. This post breaks down what that init window is actually paying for, and which parts you can move.

The short version: out of the four phases that make up a cold start, only two are under your control. The rest is AWS infrastructure that you inherit whether you like it or not.

The Four Phases

Rust Meets Serverless, Part 2: Cold Start Times

Tue, 21 Apr 2026 00:00:00 -0300

In Part 1 I covered why Rust on AWS Lambda is worth exploring and laid out the project setup. This post measures the one number that matters most for serverless latency: cold start time. To get a clean floor measurement, I used the simplest possible endpoint with no database, no external calls, and no middleware.

The Benchmark Setup

The handler is a single health endpoint built with Axum and Cargo Lambda:

Rust Meets Serverless, Part 1: Getting Started with AWS Lambda

Mon, 20 Apr 2026 00:00:00 -0300

After watching Benjamen Pyle’s talk on Rust and AWS Lambda at QCon 2025, I got curious enough to try it myself. Rust is known to be one of the best languages for building high-performing services, used across different industries where performance and stability are non-negotiable. One would expect these services to run on dedicated instances (either in the cloud or on bare-metal machines) in order to take full advantage of its benefits. However, in this post I explore whether Rust can be efficiently used in AWS Lambda.