Senior Software Engineer, Core -Source- Weights & Biases

Core Weave is The Essential Cloud for AI™. Built for pioneers by pioneers, Core Weave delivers a platform of technology, tools, and teams that enables innovators to build and scale AI with confidence. Trusted by leading AI labs, startups, and global enterprises, core Weave combines superior infrastructure performance with deep technical expertise to accelerate breakthroughs and turn compute into capability. Founded in 2017, Core Weave became a publicly traded company (Nasdaq: CRWV) in March 2025.

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At marimo, we’re on a mission to make the world’s best open‑source programming environment for working with data, together with a world‑class, scalable, and performant cloud‑hosted counterpart. marimo is a reinvention of the Python notebook — it feels like a next‑gen reactive Python notebook, but is stored as pure Python that can be versioned with Git, deployed as a data app, run as a script, and reused as a module.

Incubated initially with scientists at Stanford, marimo is now used by leading companies, labs, and universities around the world, with millions of downloads since launch and over 17,000 stars on our Git Hub repository.

The marimo core open source team develops and maintains the marimo open source notebook. Today, this includes the marimo editor frontend, the marimo backend which includes the core dataflow compiler and runtime, an intermediary server, the marimo library, and an ecosystem of related projects, such as a VS Code extension, codemirror extensions, and more. This team has the crucial role of shepherding the future of one of Python’s fastest growing and most impactful open‑source projects.

As a senior software engineer on marimo’s core open‑source team, you’ll take ownership of projects across marimo’s open‑source ecosystem, focusing on marimo’s backend and its Python ecosystem. You will influence critical decisions on library design, making sure our APIs remain simple yet composable; you’ll also design new capabilities that push the boundaries of interactive computing without complicating the user experience. You’ll work in the open, at a fast pace — engaging promptly and empathetically with a large and vocal community of users and contributors, triaging their issues and reading between the lines to understand their unstated needs.

All the while, you’ll exercise judgment to balance the needs of our community with our own roadmap and vision.

• 4+ years of experience in software engineering
• Proficiency in Python, with strong fundamentals that are language agnostic
• Proficiency in computer systems, including parallel computing (threading, multiprocessing), concurrency (asynchronous programming), basic networking/inter‑process communication
• Experience in library design and/or open‑source development
• Strong communication skills, written and verbal

• A passion for and experience building developer tools, especially for AI, ML, or data
• A passion for working with data, with the ability to empathize with practitioners and researchers in AI, ML, data engineering, NLP, or other quantitative work
• An eye for visual and interaction design, with an emphasis on simplicity
• You find enjoyment in connecting with users and community daily
• Proficiency in Typescript, or a willingness to learn
• Experience with AI engineering, including MCP and agents
• Experience with SQL, databases, and data engineering
• Experience with at least one systems language, such as C or Rust

We believe in investing in our people, and value candidates who can bring their own diversified experiences to our teams – even if you aren’t a 100% skill or experience match. Here are a few qualities we’ve found compatible with our team. If some of this describes you, we’d love to talk.

• You love crafting developer tools, especially for AI, ML, or data
• You’re curious about the day‑to‑day work of AI/ML/data engineers, researchers, and scientists
• You enjoy building in the open and engaging with your users

The base salary range for this role is $165,000 to $242,000. The starting salary will be determined based on job‑related knowledge, skills,…