Concurrency

By default the engine processes one run at a time. Raise concurrency to process multiple runs in parallel per tick:

const engine = createEngine({
  storage,
  workflows: [orderWorkflow],
  concurrency: 5, // process up to 5 runs in parallel per tick (default: 1)
})

With concurrency: 5, each tick claims up to 5 pending (or reclaimable) runs and executes them concurrently.

What runs in parallel

• Different runs run in parallel, up to concurrency.
• Steps within a single run still execute sequentially — prev flows from one step to the next. To parallelize work inside a run, use .parallel().

Each claimed run is leased and heartbeated independently, so one slow run doesn't endanger the others' leases.

Picking a value

concurrency bounds how many runs a single engine instance works on at once. Size it to your workload — I/O-bound steps (API calls, DB writes) tolerate higher concurrency than CPU-bound ones. Because claims are leased, you can also run multiple engine instances against the same storage; each claims its own runs and they share the work safely.