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Building Durable Workflows From Scratch in JavaScript

Durable workflows - workflows that checkpoint their state to automatically recover from failure - enable developers to build reliable code faster and dramatically reduce the severity of production incidents. Most workflow systems require you to set up a bunch of infrastructure, but that’s not necessary! In this talk, we’ll show you how to build durable workflows in pure JavaScript, as a library any application can import.

This talk has been presented at JSNation US 2025, check out the latest edition of this JavaScript Conference.

FAQ

Durable workflows in JavaScript are processes that regularly checkpoint the state of a program, allowing it to recover from failures by restoring from the last completed step, similar to save points in video games.

Building reliable systems is challenging because any step in a complex application can fail due to process crashes, resource limits, timeouts, external API failures, or AI brittleness, especially at large scales.

Durable workflows help recover from failures by checkpointing each step of a workflow. If a failure occurs, the system can use these checkpoints to restore the workflow from its last successful step, avoiding the need to restart from the beginning.

Implementing durable workflows in a Node.js application allows you to manage workflows directly within your app without relying on heavy external orchestration systems, reducing latency and complexity.

Checkpointing in durable workflows involves saving the state of each workflow step in a database, allowing the system to recover from failures by loading the workflow's last successful state.

Durable workflows prevent issues like data duplication by ensuring that each step is checkpointed and completed before proceeding, so in the event of a failure, steps are not repeated unnecessarily.

The two main methods in the durable workflow JavaScript library are 'register workflow', which registers a function as a workflow, and 'run step', which executes a function as a step in the workflow.

The library handles workflow recovery by identifying pending workflows that didn't finish, re-running them from the last completed step using checkpointed data, and continuing execution from there.

Using a lightweight durable workflow library in JavaScript allows developers to integrate reliable workflow management directly into their applications without needing complex external infrastructure, making it fast and efficient.

Yes, durable workflows can be used for a variety of applications including CI pipelines, data pipelines, and AI agents, providing reliable execution across different domains.

architecture

Peter Kraft

18 min

20 Nov, 2025

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Video Summary and Transcription

Peter discusses building durable workflows in pure JavaScript, highlighting challenges in creating reliable systems, especially in complex applications like Money Transfer. Failures can occur due to various reasons, including process crashes, resource issues, timeouts, and API failures. Durable workflows involve checkpointing for recovery, traditionally involving heavyweight external orchestration systems. Designing a JavaScript workflow library aims for simplicity and durability, enabling checkpointing directly on app servers. Implementing the library includes checkpoints for safety, recovery, and workflow integrity maintenance.

Available in Español: Construyendo Flujos de Trabajo Duraderos Desde Cero en JavaScript

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