Rust

Modal Labs built a container system from scratch in Rust to optimize for the fastest cold-start times, indicating a significant use of the Rust programming language in their core technology.

Spruce Systems is a member of the Rust Foundation, which is dedicated to stewarding the Rust programming language. Additionally, the company develops open-source software, which may include contributions to the Rust ecosystem.

Shuttle supports all major Rust frameworks, allows for the deployment of Rust services with a single annotation, and provides an open-source cloud platform that contributes to the Rust ecosystem.

Fennel's backend is primarily written in Rust, and it relies heavily on Rust-based technologies such as Tokio's async runtime and an in-house Rust-based streaming engine. This indicates that the company is significantly involved in the development and use of the Rust programming language. Additionally, Fennel employs efficient Rust services as part of its cost optimization strategies.

Phylum supports the Rust programming language and has actively contributed to the Rust ecosystem by identifying and stopping the publication of malicious packages to Crates.io.

Boundary's BAML compiler is written mostly in Rust, indicating the company's involvement in the development and use of the Rust programming language. Additionally, BAML and its VSCode extension are free and open-source, contributing to the Rust ecosystem.

Nomic Foundation develops and distributes Slang, a set of compiler APIs for Solidity code analysis, which is written in Rust.

Metana offers a Rust Bootcamp aimed at making students expert Solana blockchain developers, which indicates involvement in the development and use of the Rust programming language.

Empower built a high performance LoRA inference engine using Rust, which indicates that the company is involved in the development and use of the Rust programming language. This matches the criteria of being primarily involved in Rust and contributing to the Rust ecosystem.