GL & Booking Engine — Rules & Mapping Architecture

Single-source design document capturing the unified XRule taxonomy, versioned mapping layer, rule engine, and pluggable data/storage options (PostgresQL, Redis, RDI, Dragonfly, ScyllaDB)

0) TL;DR (high-level)

```mermaid
flowchart LR
  subgraph Sources
    T[Bank Txns\n(1.7M+)] -->|CSV/API| ING[Ingestor]
    I[Invoices\n(400k+)] -->|CSV/API| ING
    M[Manual Rules\n(User/Tenant)] -->|UI| CFG[Rule Config API]
  end

  subgraph Core
    ING --> NORM[Normalizer]
    NORM --> MAP[Mapping Layer\n(XRule Resolver)]
    CFG --> MAP
    MAP --> RE[Rule Engine]
    RE --> BOOK[Booking Generator]
    BOOK --> EV[Events/Audit Trail]
  end

  subgraph Data & Caches
    PG[(Postgres)]
    RD[(Redis/Dragonfly via RDI)]
    SC[(ScyllaDB\noptional)]
  end

  MAP --- RD
  RE --- RD
  BOOK --- PG
  EV --> PG
  PG <--> RD
  PG <--> SC
```