How Reddit Migrated Comments Functionality from Python to Go

Reddit successfully migrated its monolithic, high-traffic Comments service from legacy Python to modern Go microservices with zero user disruption. This was achieved by using a "tap compare" for reads and isolated "sister datastores" for writes, ensuring safe verification of the new code against production data. Despite challenges like cross-language serialization and database race conditions, the migration succeeded, resulting in a dramatic reduction in p99 latency for all write operations. .