Architecture

Dual Write

The pattern of writing to both an append-only event log and a materialized current-state file simultaneously to get both audit trail and fast reads.

Dual write solves a fundamental tension in file-based systems: event logs (JSONL) give you audit history and git-diffable changes, but they are slow to query. Materialized state files (JSON) give you fast reads, but lose history. The dual-write pattern writes to both on every mutation. The kanban system writes task events to tasks.jsonl (append-only, git tracks every change) and updates tasks_current.json (latest state, instant lookup). If the materialized state ever gets corrupted, you can rebuild it by replaying the event log. The JSONL file is the source of truth. The JSON file is a read-optimized projection.

Where it shows up:

Kanban task managementKnowledge graph changelogEvent sourcing patternsState recovery

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