Module checkpoint 

Workflow Checkpoint Storage Primitives (Task 6)

This module provides durable workflow state persistence as a storage primitive, NOT an orchestration framework. External frameworks (Temporal, Airflow, custom) can use this as a clean storage API for:

• Checkpoint storage: CHECKPOINT(run_id, node_id, state_blob)
• Checkpoint retrieval: RESUME(run_id)
• Run metadata

Architecture Decision

SochDB is the source of truth for state (runs/events/checkpoints). Scheduling and execution are handled by external orchestrators. This separation of concerns:

• Preserves clean API boundaries
• Avoids building a competing orchestration framework
• Enables easy integration with existing tools

Complexity

• Checkpoint write: O(S) where S is state size
• Checkpoint read: O(S)
• List checkpoints: O(log N + k) with index
• Recovery: O(S + m) where m is events since snapshot

Schema

_checkpoints/{run_id}/meta              -> RunMetadata
_checkpoints/{run_id}/nodes/{node_id}   -> CheckpointData
_checkpoints/{run_id}/events/{seq}      -> EventData

Structs

Checkpoint

A checkpoint snapshot

CheckpointMeta

Metadata about a checkpoint (without the state blob)

DefaultCheckpointStore

Default checkpoint store implementation using ConnectionTrait

RunMetadata

Metadata about a workflow run

WorkflowEvent

An event in the workflow event log

Enums

RunStatus

Status of a workflow run

Traits

CheckpointStore

Trait defining the checkpoint storage interface

Type Aliases

NodeId

Unique identifier for a node within a run

RunId

Unique identifier for a workflow run

SeqNo

Sequence number for events