Durable Workflow Snapshot

Problem

Keeping the workflow state only in process memory is enough to survive a single crash that the same process recovers from, but not deploys that replace the binary, host failures that move work elsewhere, or pauses long enough that the original worker is gone. Without writing the full state out to durable storage at known checkpoints, every deploy or host loss vaporises in-flight runs and the work restarts from zero. The team is forced to choose between short workflows that fit in one process lifetime or accepting that long-running workflows will routinely lose hours of progress.

Solution

Treat the workflow runtime as a state machine whose state is fully serialisable. At checkpoints (after every step, on suspend, before risky actions) write a snapshot — `{step_index, local_state, awaited_signals, history}` — to a pluggable storage provider (Postgres, S3, Redis, vendor-managed). To resume, load the snapshot, rehydrate state, and continue from the recorded step. Version snapshot schemas; refuse to resume incompatible versions rather than corrupt the run. Pair with agent-resumption (the broader pattern), replay-time-travel (the auditor view), and provenance-ledger (linking snapshots to outputs).

When to use

• Runs span deploys (anything longer than a typical release cycle).
• Workflows may wait minutes-to-hours on external signals.
• Host loss must not lose user work.
• An audit trail of intermediate state is required.