Temporal — Workflow as Code
Temporal is the prior art every durable-execution framework is measured against. If you're picking a workflow runtime, evaluating WDK, or reading a paper on durable execution, the Temporal model — workflows + activities + signals + timers + event history — is the vocabulary. Even if you choose WDK or Step Functions for a specific stack, understanding Temporal makes their tradeoffs legible (sandbox restrictions vs full Node, hosted runtime vs self-host, JSON DSL vs code).
What It Defines
Open-source durable-execution platform (originally a fork of Uber's Cadence) maintained by Temporal Technologies. The Temporal Server is MIT-licensed; SDKs ship for TypeScript, Go, Java, Python, .NET, PHP, and Ruby. Workflows are deterministic functions whose every blocking call (activity, timer, signal, child workflow) is recorded to an event history; on replay the SDK fast-forwards by re-feeding the history. Activities (the equivalent of WDK steps) run with full runtime access and arbitrary retries. Temporal pioneered the modern durable-execution model that Workflow DevKit, Cloudflare Workflows, Restate, and DBOS now adapt to their own runtimes.
Canonical (Normative)
Convenient (Practical)
Related References
Company behind the Temporal open-source durable-execution platform (originally a fork of Uber's Cadence). Publishes the Temporal Server (MIT) and SDKs in TypeScript, Go, Java, Python, .NET, PHP, and Ruby. Temporal popularized the modern "workflow as code" pattern — deterministic replay over an event-sourced history — that Workflow DevKit, Cloudflare Workflows, Restate, and DBOS all draw from.
Related Specs
WDK is the durable-execution model arriving inside the JavaScript ecosystem proper: instead of writing a state machine, you write `async` code with two extra string directives and you get crash-safe, resumable, retry-aware, observable workflows. If you're building AI agents, multi-step background jobs, human-in-the-loop flows, or anything that previously needed BullMQ + a state machine + careful idempotency, WDK collapses that into a single mental model. Even if you don't pick WDK specifically, the directives + replay model are the durable-execution pattern Temporal pioneered and Cloudflare/Restate/DBOS now ship — knowing one teaches you the rest.
If you remember one thing about durable execution, remember this: workflow code runs many times and the event log decides what's real. That single fact explains every WDK rule — why steps must be idempotent, why you can't read `Date.now()` directly in a workflow, why parameters are passed by value, why mutating an object inside a step doesn't propagate, and why bundlers occasionally bite you. Internalize the replay model and the rest of WDK (and Temporal, and Cloudflare Workflows) becomes obvious.
Step Functions is the most widely deployed durable-execution runtime, and ASL is the JSON contract under it. If you ever need a state machine to coordinate Lambdas, run a Saga, or fan out parallel work in AWS, you'll write ASL — and unlike WDK or Temporal it's a declarative DSL, not code, which is both its strength (visualizable, statically inspectable) and its weakness (loops and dynamic control flow are awkward). Worth knowing as the canonical "workflow as JSON" comparison point.
If your stack is on Cloudflare Workers, Cloudflare Workflows is the native durable-execution option — no extra infra, billed alongside Workers, and able to call other Workers/D1/R2/Queues directly. Useful comparison point for WDK: same model, different runtime constraints. Worth knowing both to pick the right tool and to recognize the durable-execution pattern as it spreads across edge platforms.
The deeper pattern under every durable-execution runtime. If you understand event sourcing, you understand why a WDK workflow function runs over and over and gets the same answer, why steps must be deterministic on the workflow side, and why activities/steps can be retried freely. Also useful in its own right — for ledgers, audit logs, CQRS read models, and any system where "how did we get to this state?" is a real question.