Reddit has re‑engineered its comment service, moving from a monolithic Python stack to a domain‑specific Go microservice. The migration halved p99 latency for critical write operations, reduced downtime during peak traffic, and laid the groundwork for modernizing all four core models. The story illustrates how careful staged rollout, tap‑compare testing, and data‑store isolation can unlock performance gains in a high‑write, highly‑available system.