Sandbox resourcing: burst, don't reserve

Modal argues that fixed-resource reservations fit poorly with bursty Sandbox workloads, since a typical Sandbox spends more than half its life using under 6% of its peak CPU, so users over-reserve and pay for peak constantly. Modal's Sandboxes now burst by default from a base request of 0.125 cores and 128 MiB, with active-resource pricing billed each second for what is used, and the company cites 58% savings versus a fixed-size reservation on an illustrative 20-minute coding agent task. It also describes an OOM SLO of below 0.0001% per minute for bursting Sandboxes under 8 GiB and tools like exit snapshots and the termination reasons SDK to reduce eviction impact.