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Readiness Probes

1 post about Readiness Probes. Every summary links to the original.

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Unpacking sandbox startup latency: why started ≠ ready
Sandbox startup benchmarks measure container boot time, but in production application-level initialization after boot dominates, making container boot the smallest variable. Modal defines a lifecycle with events Created, Scheduled, Started, and Ready, where Ready indicates completion of tasks like git pulls or dependency installs. The gap between Started and Ready can be multiple seconds, directly affecting user-perceived latency for coding agents needing cloned repos and running services. To reduce perceived latency, Modal recommends warm pools that pre-initialize sandboxes using a Queue, combined with Directory Snapshots for per-project customization without rebuilding the environment. Readiness Probes, now generally available, allow defining a shell command that exits 0 or a TCP port that accepts connections, with wait_until_ready() blocking until the sandbox is truly ready, simplifying warm pool producer code and providing dashboard events for observability.

The best engineering reads, once a week.

Topic

1 post about Readiness Probes. Every summary links to the original.

Paid picks we use ourselves. Links carry a referral code — a subscription through one earns us a commission at no extra cost to you.

Newest first

Modal
Unpacking sandbox startup latency: why started ≠ ready
Sandbox startup benchmarks measure container boot time, but in production application-level initialization after boot dominates, making container boot the smallest variable. Modal defines a lifecycle with events Created, Scheduled, Started, and Ready, where Ready indicates completion of tasks like git pulls or dependency installs. The gap between Started and Ready can be multiple seconds, directly affecting user-perceived latency for coding agents needing cloned repos and running services. To reduce perceived latency, Modal recommends warm pools that pre-initialize sandboxes using a Queue, combined with Directory Snapshots for per-project customization without rebuilding the environment. Readiness Probes, now generally available, allow defining a shell command that exits 0 or a TCP port that accepts connections, with wait_until_ready() blocking until the sandbox is truly ready, simplifying warm pool producer code and providing dashboard events for observability.

The best engineering reads, once a week.