Checkly Rewrote a 92M-Message-a-Day Node Service in Go With AI Agents: Zero Incidents

rseroter · x · 2026-09-09

Checkly used Claude Code to rewrite its Results Daemon—a Node.js service processing 92M messages/day, including 40M check results—from Node to Go. The result shipped with zero incidents, 70% fewer running pods, and lighter database load. The key was building a test harness before the agent wrote a line of code; Go's stronger type system also proved a better fit for agents, guarding against regressions and enabling faster, safer shipping. A detailed, reusable playbook for agentic rewrites of critical legacy services.

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