6740a017c7
- Phase 6: Ingest pipeline (CSV/JSON → schema detect → Parquet → catalog) - Phase 7: Vector index + RAG (embed → HNSW → semantic search → LLM answer) - Phase 8: Hot cache + incremental updates (MemTable, delta files, merge-on-read) - ADR-008 through ADR-011: embeddings as Parquet, delta files not Delta Lake, schema defaults to string, not a CRM replacement - Staffing company reference dataset (286K rows, 7 tables) - Honest risk assessment: vector search at scale and incremental updates are hard Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
57 lines
3.9 KiB
Markdown
57 lines
3.9 KiB
Markdown
# Architecture Decision Records
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## ADR-001: Object storage as source of truth
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**Date:** 2026-03-27
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**Decision:** All data lives in S3-compatible object storage. No traditional database.
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**Rationale:** Eliminates DB operational overhead, enables infinite scale at storage tier, forces clean separation of data and metadata.
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## ADR-002: Catalog metadata persistence
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**Date:** 2026-03-27
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**Decision:** catalogd persists manifests as Parquet files in object storage. In-memory index rebuilt on startup.
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**Rationale:** No external DB dependency. Storage is already the source of truth. Write-ahead pattern ensures consistency.
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## ADR-003: Real models only (no mocks)
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**Date:** 2026-03-27
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**Decision:** AI sidecar hits Ollama with real models from Phase 3 onward. No stub/mock endpoints.
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**Rationale:** Local Ollama instance available with nomic-embed-text, qwen2.5, mistral, gemma2, llama3.2. Mocks hide integration bugs.
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## ADR-004: Python sidecar as Ollama adapter
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**Date:** 2026-03-27
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**Decision:** Python FastAPI sidecar is a thin HTTP adapter over Ollama's API. No model loading in Python.
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**Rationale:** Ollama handles model lifecycle, GPU scheduling, caching. Sidecar stays stateless and lightweight — no torch/transformers deps.
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## ADR-005: HTTP-first, gRPC later
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**Date:** 2026-03-27
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**Decision:** All inter-service communication uses HTTP through Phase 4. gRPC migration in Phase 5.
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**Rationale:** HTTP is simpler to debug, test, and iterate on. gRPC adds protobuf compilation and streaming complexity before APIs stabilize.
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## ADR-006: TOML config over environment variables
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**Date:** 2026-03-27
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**Decision:** System configuration via lakehouse.toml file, with sane defaults for all values.
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**Rationale:** Config files are versionable, self-documenting, and support structured data. Env vars remain available as overrides. System must be restartable from repo + config alone.
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## ADR-007: Dual HTTP+gRPC on gateway
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**Date:** 2026-03-27
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**Decision:** Gateway serves HTTP on :3100 (external) and gRPC on :3101 (internal). Both run in the same process.
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**Rationale:** Single binary simplifies deployment. HTTP stays for browser/curl access. gRPC provides typed contracts for service-to-service calls. No premature microservice split.
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## ADR-008: Embeddings stored as Parquet, not a proprietary vector DB
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**Date:** 2026-03-27
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**Decision:** Vector embeddings stored as Parquet files (doc_id, chunk_text, vector columns). Vector index (HNSW) serialized as a sidecar file.
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**Rationale:** Keeps all data in one portable format. No vendor lock-in to Pinecone/Weaviate/Qdrant. Vectors are queryable via DataFusion like any other data. Trade-off: brute-force search is fine up to ~100K vectors; HNSW needed beyond that.
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## ADR-009: Incremental updates via delta files, not Delta Lake
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**Date:** 2026-03-27
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**Decision:** Updates append to delta Parquet files. Queries merge base + deltas at read time. Periodic compaction merges deltas into base. Single-writer model (no concurrent writers).
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**Rationale:** Full ACID over Parquet (Delta Lake/Iceberg) is a multi-year project. Our use case is single-writer (one ingest pipeline) with read-heavy workloads. Merge-on-read with compaction is sufficient and dramatically simpler.
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## ADR-010: Schema detection defaults to string
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**Date:** 2026-03-27
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**Decision:** Ingest pipeline infers column types from data. When ambiguous or mixed, defaults to String rather than failing.
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**Rationale:** Legacy data is messy. A column with "123", "N/A", and "" is a string, not an integer. Downstream queries can CAST as needed. Better to ingest everything than reject on type errors.
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## ADR-011: This is not a CRM replacement
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**Date:** 2026-03-27
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**Decision:** The lakehouse is the analytical layer BEHIND operational systems. It ingests exports, not live data. CRM/ATS stays for daily operations.
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**Rationale:** Operational systems need single-record CRUD, permissions, UI workflows. The lakehouse answers cross-cutting questions that no single operational system can. They complement, not compete.
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