ADR 0006 — Storage backends

• Date: 2026-08-07 · Status: Accepted

Context

Knovaryn must run local (SQLite + filesystem) and team (PostgreSQL + S3) without locking into a single backend (spec §0.1, §21).

Decision

• Database: SQLAlchemy 2 async + Alembic. SQLite default (WAL, foreign keys, documented local concurrency); PostgreSQL production (asyncpg).
• Artifact store: content-addressed immutable bytes plus manifest metadata. Local CAS default; S3-compatible adapter behind the s3 extra. Both implement the same ArtifactStore port: streaming puts, checksum verification, atomic commit (blob before manifest), legal hold, and repair support.
• Database rows reference committed artifact hashes; an outbox/transactional finalization pattern and a repair command reconcile orphaned rows/objects.

Consequence

Local-first by default; team deployment is a config change, not a code fork.