Unpacking sandbox startup latency: why started ≠ ready | Modal Blog

What this post added

Introduced Readiness Probes as a first-class feature for sandboxes, allowing users to define custom checks (shell commands or TCP ports) to determine when a sandbox is fully initialized and ready for use. This feature is integrated with `sandbox.wait_until_ready()` and provides a new 'ready' event in the dashboard timeline for enhanced observability of the sandbox startup lifecycle. The post also discusses the optimization of perceived latency through warm pools and the use of Directory Snapshots, highlighting how Readiness Probes simplify the management of these warm pools by providing a reliable signal for when a sandbox is truly ready to be handed out.