How Monk migrated 100+ workflows from Inngest to Temporal

Francesco Coacci, a founding engineer at Monk, discusses the strategic migration of workflows from Inngest to Temporal in their AI-powered accounts receivable platform. The shift was necessitated by scalability issues with Inngest, which initially facilitated rapid development but eventually became cumbersome as the number of asynchronous jobs exceeded a hundred. The migration was methodically executed in stages, ensuring both systems ran concurrently through a series of reversible pull requests, each following a strict four-step process: characterizing the existing workflow, scaffolding with Temporal, transitioning operations via a feature flag, and finally removing the Inngest job post-stability. This approach allowed for continuous testing and validation, minimizing disruption and maintaining service consistency. Key challenges included managing concurrency and ensuring workflow determinism—elements that required custom solutions due to Temporal's distinct architecture. The article emphasizes the importance of incremental migration, thorough testing, and maintaining dual systems to ensure a seamless transition, ultimately resulting in improved visibility, idempotency, and operational isolation within the platform.