Files
alkblobs/docs/architecture
glm-5.3-flash 395d58cf3f docs(architecture): ADR-007 — two kv engines (sqlite + postgres) behind one trait
Dissolve OQ-10's circular "standing offer" framing and record the
engine decision the POC evidence already supported:

- ADR-007 (new): kv tier ships sqlite (default) + postgres (feature
  `postgres`, default-off), constructor-selected per node; records the
  deployment economics (classical kv+fs+relational downstream stack
  collapses to one relational engine + fs), the pg impl contract
  (POC #5 B5 posture deltas), the CI sweep-safety gate under
  --all-features, redb ruled out (POC #6), and posture defaults as
  deferred cost in the ADR-006 pattern
- ADR-003: amended status (engine pin widened by ADR-007); kv entry
  notes the widened engine set
- ADR-004: reconciliation note — the "two backends" count is tiers,
  not engines
- backends-and-dispatch.md: tier≠engine distinction, pg engine
  section, co-tenancy note (same-file consumer writes share sqlite's
  single-writer ceiling), substitution-door precedent
- open-questions.md: OQ-10 resolved-by-ADR-007, with the
  why-this-is-not-Schrödinger's-code record (a deployment running
  alkblobs cannot pre-exist the pg engine — OQ-09 precedent); parked
  index narrowed to OQ-07/OQ-08
- overview.md: layer map + dependency posture reflect the `postgres`
  feature; README.md: ADR-007 in tables + corollary applications
- phase-0.md / pg+redb findings: promotion + supersession notes

Trigger framing survives only as deployment guidance (which engine a
node chooses — topology, not throughput), not as a gate on the crate's
own work.

Verified: cargo test, clippy --all-targets -D warnings, fmt --check.
Docs-only change (Phase 1 architecture); no implementation yet.
2026-10-02 19:29:42 +00:00
..

status, last_updated
status last_updated
draft 2026-10-02

alkblobs — Architecture

Current State

Phase 1 (Architecture). Phase 0 (Exploration) converged — see docs/research/phase-0.md for the vision, the evidence trail, and the POC register (all POCs passed or were absorbed; POC code lives in standalone crates (/workspace/alkblobs-trait-poc, /workspace/alkblobs-largeblob-poc); findings live in docs/research/). No implementation exists yet (src/lib.rs is a placeholder).

The converged Phase 0 posture has been promoted into the specs and ADRs below. Two framing corrections from the convergence review are captured there — not inherited as hedges:

  • ADR-001 makes the substrate posture explicit: the store layer carries no alkcall dependency by design — which is conformance to the family pattern, not deviation from it — and the ops surface rides alkcall, feature-gated.
  • ADR-004 fixes the "two backends" framing: the crate ships exactly two backends (kv small / fs large — both required by measured scale economics); the path→hash mapping layer (the alkfs/alknet "vfs" shape) is a consumer-layer concern and must never become a third backend.
  • ADR-007 widens the kv tier's engine set rather than hedging it: sqlite (default) + postgres (feature-gated) behind one trait. The deployment economics this records: a downstream node (git server, vfs) classically needed three storage systems — kv + fs + relational — and this design collapses them to one relational engine + fs, with the engine a per-node constructor choice. Resolved from evidence in hand (POCs #3/#5/#6); the would-be "deployment trigger" framing was caught at review as circular hedging (a deployment running alkblobs cannot pre-exist the engine) and closed on the OQ-09 precedent.

Architecture Documents

Document Scope Status
overview.md Purpose, consumers, layer map, dependency posture draft
hashing-and-keys.md Canonical hash, key encoding (the one-way door) draft
store-api.md Store facade: put/get/stat/range/pin/batch/sweep surface, errors, invariants draft
backends-and-dispatch.md Backend trait contract, shipped backends, size-threshold dispatch draft
gc-and-namespaces.md Pooled CAS, liveness seams, mark-and-sweep, delete windows draft
ops-surface.md alkcall-backed have/need + fetch/put ops, ACL mapping draft
open-questions.md Centralized OQ tracker (incl. promoted Phase 0 register) draft

Decision Records

ADR Decision Status
001 Substrate posture & ops-surface placement (conformance, not deviation) Accepted
002 Canonical hash + key encoding (the wire-format ADR; precedes any consumer) Accepted
003 Backend contract, shipped backends, dispatch policy Accepted
004 Exactly two backends; manifest layers stay above Accepted
005 Pooled CAS, liveness seams, mark-and-sweep, delete windows Accepted
006 Whole-blob verification; transfer encoding excluded by scoping Accepted
007 Two kv engines (sqlite + postgres) behind one trait; constructor-selected Accepted

Open Questions

Tracked in open-questions.md. The Phase 0 register (OQ-BL-01..06) is promoted there with its resolutions; two questions remain parked — OQ-07/OQ-08 externally-owned (alkgit seam mapping, alkfs intake; carried for visibility, gating nothing here). OQ-09 (namespace-visibility default) resolved closed-by-default; OQ-10 (second kv engine) resolved by ADR-007. Deferral policy (the "Schrödinger's code" rule): a decision this crate needs before shipping may not be deferred on a dependency that is itself waiting for this crate to exist. Two parking kinds remain legitimate: deferred(scope) on a deciding fact that exists independently of this crate, and externally-owned questions (how a consumer maps onto this crate) that gate no decision here — full definitions in the header of open-questions.md. A corollary worth restating, because it recurs: a fact this crate must create (its own first deployment, its own first consumer) is never a deciding input — decisions stand on evidence in hand, and future needs reopen via named requirements, not via waiting. (Corollary applications so far: OQ-09 and OQ-10 both resolved on it.)

Lifecycle

Spec docs: draft → reviewed → stable → deprecated. A doc moves reviewed when every crate-owned open question it references resolves and an architecture review pass clears it — externally-owned OQs (OQ-07/OQ-08) gate nothing here by definition and do not block the lifecycle; their outcomes arrive through their owners' processes. stable when implementation verifies against it; deprecated when superseded (kept for reference). ADRs use a separate status set (Accepted | Proposed | Deprecated | Superseded), defined per ADR file. This tree is in draft pending the first architecture review cycle.