How I replaced a long-lived Cloudflare Container with a one-shot Cloudflare Sandbox, deleted most of the control-plane code, and let an agent do the heavy lifting in less than an hour of my own time.

Kent C. Dodds is a well-known software engineer, educator, and open-source advocate renowned for his expertise in JavaScript and React. Through his blog, courses, and conference talks, Kent shares insights, best practices, and practical tips on front-end development, testing, and software engineering. Developers can learn from Kent's extensive experience and deep understanding of the JavaScript ecosystem, gaining  insights into building modern web applications with React and other technologies.

Kent C. Dodds

Kent C. Dodds shares how he replaced a Cloudflare Container-based FFmpeg audio pipeline with Cloudflare Sandboxes, eliminating heartbeat/shutdown coordination plumbing. The new design uses a one-shot sandbox.exec() call directly from the queue worker, keeping R2 credentials in the worker and passing only presigned URLs to the sandbox. The sandbox image is minimal: base Cloudflare sandbox image plus FFmpeg and a shell script. Two production bugs surfaced post-merge — a sandbox ID length limit (63 chars max) and a broken Dockerfile that replaced the required Cloudflare sandbox runtime with a plain Debian base. Both were diagnosed and fixed with help from a Cursor agent and the Cloudflare MCP server. The entire migration, including two PR iterations, took under an hour of the author's own time.

Simplifying Containers with Cloudflare Sandboxes

What the merged version actually looks like