Migrating our Email API to Go

Resend migrated its core email API from Node.js to Go over a seven-week period to improve performance and reliability under heavy traffic loads. During a 50 percent rollout, the Go service reduced median latency, decreased memory usage per task by about 86 percent, and used roughly 62 percent less CPU per request. Engineering decisions during the rewrite focused on maintaining backward compatibility, matching existing idempotency and rate-limiting behavior, and porting specific HTML-to-text conversion logic. Open article →