Back Engineering July 16, 2026•10 minute readAt Modal, we build sandboxes, among other things. Agents run in sandboxes, and agents are eating software. Today, Modal runs millions of sandboxes per day, supports up to fifty thousand concurrent sandboxes per customer, and supports a variety of use cases at scale, from reinforcement learning to background agents.Increasingly, our users require more and more sandboxes, created at higher and higher rates. Reinforcement learning can require running mil...