Enterprise Wholesale ERP – Multi-Tenant Commerce Platform

At a Glance

The Problem

Wholesale import businesses in Bangladesh and similar markets run complex operations across multiple legal entities:

• A parent company handles international procurement, customs clearance, and warehouse stock
• Sister concerns (child tenants) run wholesale desks, B2B storefronts, and dropship reseller networks
• External investors fund shipment batches and need yield visibility
• B2B customers order through branded storefronts with their own wallets and credit limits

Pain points before TradeflowBD

flowchart TD
    subgraph Before ["Before: Fragmented Operations"]
        A["Spreadsheets for costing & demand"] --> B["Manual shipment tracking"]
        B --> C["Separate stock counts per desk"]
        C --> D["Shadow accounting in Excel"]
        D --> E["No single view of AR / payables"]
        E --> F["Data leakage risk across tenants"]
    end

The core question

How do you build one SaaS platform where a parent company pools physical stock, multiple child desks sell from allocations, customers shop online, investors see yield — and no tenant can ever see another tenant’s data?

The Solution

TradeflowBD is a plug-and-play multi-tenant ERP that covers the full wholesale lifecycle:

Pre-Order Costing → Inbound Shipment & Landed Cost → Warehouse Pooling
    → Multi-Desk Selling (Wholesale / Storefront / Dropship)
        → Universal Wallet Settlement → Treasury & Investor Reporting

One platform. Four login surfaces. Database-enforced isolation. Configuration-driven modules.

flowchart LR
    subgraph Input ["Demand & Procurement"]
        PBC["Pre-Order Costing"]
        SHIP["Inbound Shipments"]
    end

    subgraph Pool ["Parent Warehouse"]
        STOCK["Global Stock Pool"]
        LOC["4-Tier Bin Locations"]
    end

    subgraph Sell ["Multi-Desk Selling"]
        WS["Wholesale POS"]
        SHOP["B2B Storefront"]
        DS["Dropship Desk"]
    end

    subgraph Finance ["Consolidated Finance"]
        WALLET["Universal Wallet"]
        TREASURY["Treasury Reports"]
        INV["Investor Yield"]
    end

    PBC --> SHIP
    SHIP --> STOCK
    STOCK --> LOC
    STOCK --> WS
    STOCK --> SHOP
    STOCK --> DS
    WS --> WALLET
    SHOP --> WALLET
    DS --> WALLET
    WALLET --> TREASURY
    WALLET --> INV

Architecture

High-level system design

flowchart TB
    subgraph Clients ["Client Surfaces"]
        PLATFORM["Platform Scope<br/>/superadmin/*"]
        APP["App Scope<br/>/:slug/app/*"]
        SHOP["Shop Scope<br/>/:slug/shop/*"]
        INVESTOR["Investor Scope<br/>/:slug/investor/*"]
    end

    subgraph Frontend ["Frontend — Vue 3 / Quasar SPA"]
        ROUTER["Vue Router + Scope Guards"]
        PERMS["Module Permission Guard"]
        TQ["TanStack Query<br/>Server State Cache"]
        PINIA["Pinia Stores"]
        MODULES["20+ Domain Modules<br/>page → store → service → repository"]
    end

    subgraph Backend ["Backend — Supabase"]
        AUTH["Supabase Auth<br/>Google OAuth"]
        RLS["Row-Level Security<br/>200+ Policies"]
        RPC["Atomic RPCs<br/>300+ Functions"]
        RT["Realtime Channels"]
        DB["PostgreSQL 15+"]
    end

    subgraph Pipeline ["Data Pipeline"]
        PYTHON["Python ETL<br/>Price Check / WTS Sync"]
        EXCEL["ExcelJS Bulk Import"]
    end

    PLATFORM & APP & SHOP & INVESTOR --> ROUTER
    ROUTER --> PERMS --> MODULES
    MODULES --> TQ & PINIA
    TQ --> RPC
    PINIA --> RPC
    RPC --> RLS --> DB
    AUTH --> RLS
    RT --> TQ
    PYTHON --> DB
    EXCEL --> MODULES

Deployment topology

flowchart LR
    USER["Users"] --> CF["Cloudflare Pages<br/>Quasar SPA Build"]
    CF --> SB["Supabase Cloud<br/>PostgreSQL + Auth + Storage"]
    DEV["Developers"] --> DOCKER["Local Supabase<br/>Docker"]
    DOCKER --> MIGRATE["980+ Migrations<br/>Replay Before Deploy"]
    MIGRATE --> SB
    PYTHON["Python ETL Scripts"] --> SB
    MOBILE["Capacitor Android<br/>Barcode Scanner"] --> CF

Multi-Tenant Model

The hardest design problem was parent–child hierarchy with shared stock but isolated desks.

flowchart TD
    subgraph Platform ["Platform Superadmin"]
        SA["Superadmin"] --> TENANTS["Tenant Registry"]
    end

    subgraph Parent ["Parent Company (parent_id = NULL)"]
        P["Parent Workspace"]
        P --> PHYS["Physical Stock (global_stocks)"]
        P --> SHIPMENTS["Inbound Shipments"]
        P --> INVESTORS["Investor Capital Pools"]
        P --> REPORTS["Consolidated Treasury"]
    end

    subgraph Children ["Sister Concerns (parent_id = parent.id)"]
        P -->|Virtual Allocations| C1["Child A — Wholesale Desk"]
        P -->|Virtual Allocations| C2["Child B — Storefront & Dropship"]
        C1 --> INV1["Sales Invoices & Customers"]
        C2 --> SHOP1["B2B Storefront Orders"]
    end

    TENANTS --> P

Ownership rules

Key rule: Hierarchy is strictly one level deep. A child cannot have children. A parent with children cannot be assigned a parent.

Four Application Scopes

One codebase, four distinct user experiences — each with its own auth flow, layout theme, and permission model.

flowchart LR
    URL["Incoming URL"] --> R1{Route Match}
    R1 -->|"/superadmin/*"| S0["Platform<br/>Tenant provisioning"]
    R1 -->|"/:slug/app/*"| S1["App<br/>ERP backoffice"]
    R1 -->|"/:slug/shop/*"| S2["Shop<br/>B2B storefront"]
    R1 -->|"/:slug/investor/*"| S3["Investor<br/>Read-only portal"]

Permission & Module Gating

Features are not hardcoded per tenant. A three-layer guard decides access at runtime.

flowchart TD
    REQ["User attempts action"] --> M{"1. Module enabled?<br/>(tenant_modules)"}
    M -- No --> DENY["Access Denied"]
    M -- Yes --> A{"2. User is admin?<br/>(memberships.role)"}
    A -- Yes --> ALLOW["Access Granted"]
    A -- No --> G{"3. Has action grant?<br/>(module_actions)"}
    G -- Yes --> ALLOW
    G -- No --> DENY

Action grant hierarchy

view    → Read tables and detail pages
create  → Add new records
edit    → Modify drafts and configs
delete  → Soft-delete to Trash
manage  → Admin overrides, voiding, settings
order   → Customer cart placement (shop scope only)

Navigation menus and dashboard widgets are filtered dynamically — a tenant without the thrift module never sees thrift routes, even if the code exists in the bundle.

Core Technical Decisions

Decision 1 — Database-level isolation, not app-level filtering

flowchart LR
    APP["Vue App"] -->|"JWT with tenant context"| SB["Supabase Client"]
    SB --> RPC["RPC / Direct Query"]
    RPC --> RLS["RLS Policy Check<br/>membership_has_module_action()"]
    RLS -- Pass --> DATA["Tenant-Scoped Rows"]
    RLS -- Fail --> EMPTY["Zero Rows Returned"]

Decision 2 — Parent-owned stock, virtual child allocations

Decision 3 — Atomic RPCs for all complex writes

sequenceDiagram
    participant UI as Vue Component
    participant TQ as TanStack Query
    participant RPC as PostgreSQL RPC
    participant DB as Database

    UI->>TQ: Mutation (place order)
    TQ->>RPC: create_shop_order_from_cart()
    RPC->>DB: BEGIN
    RPC->>DB: Allocate stock (ATP check)
    RPC->>DB: Create order + items
    RPC->>DB: Record wallet ledger entry
    RPC->>DB: COMMIT
    RPC-->>TQ: Order result
    TQ-->>UI: Optimistic cache patch

Decision 4 — Universal Wallet with no shadow ledgers

flowchart TD
    subgraph OneWallet ["One-Wallet Rule"]
        KEY["(parent_tenant_id, entity_type, entity_id, currency)"]
    end

    subgraph Entities ["Entity Types"]
        TENANT["tenant — company cash"]
        CUSTOMER["customer — AR / store credit"]
        VENDOR["vendor — payables"]
        COURIER["courier — COD collections"]
        CARGO["cargo_company — freight payables"]
        INVESTOR["investor — capital pool"]
    end

    KEY --> TENANT & CUSTOMER & VENDOR & COURIER & CARGO & INVESTOR

    subgraph PnL ["Read-Side P&L (No Shadow Ledger)"]
        SNAP["Immutable cost snapshots<br/>on invoice lines"]
        SNAP --> MARGIN["Invoice Margin Report"]
        SNAP --> SHIPPNL["Shipment Batch P&L"]
    end

Decision 5 — TanStack Query for server state orchestration

Decision 6 — Domain-modular schema split

Domain Modules

mindmap
  root((TradeflowBD))
    Governance
      Tenant Auth & RBAC
      Access Control
      Operational Data Reset
      Soft Delete / Trash
    Procurement
      Inbound Shipments
      Landed Cost Engine
      Warehouse Locations
      Stock Movements
    Commerce
      Wholesale POS
      B2B Storefront
      Dropship Finance Hub
      Catalog Negotiation
    Finance
      Universal Wallet
      Treasury Reports
      Customer Dues
      Courier COD Remittance
    Verticals
      Thrift (Second-Hand Retail)
      Koba (UK Cross-Border)
      Product-Based Costing
    Capital
      Investor Profiles
      Shipment Allocations
      Yield Reporting

Module highlights

Dropship Finance Hub — Example End-to-End Flow

Shows how procurement, commerce, and wallet layers connect in one atomic workflow.

sequenceDiagram
    participant Reseller as Dropship Reseller (Shop)
    participant Desk as Dropship Desk (App)
    participant RPC as PostgreSQL RPCs
    participant Stock as Parent Stock Pool
    participant Wallet as Universal Wallet

    Reseller->>RPC: place_dropship_order()
    RPC->>Stock: Hold stock (ATP reservation)
    RPC->>Wallet: Record customer receivable
    RPC-->>Reseller: Order confirmed

    Desk->>RPC: confirm_dropship_delivered()
    RPC->>Stock: Release hold, deduct quantity
    RPC->>Wallet: Record courier COD collection
    RPC->>Wallet: Record merchant payout
    RPC-->>Desk: Settlement complete

Landed Cost Engine

Every margin report, invoice line, and investor yield calculation depends on accurate unit costs stamped at shipment finalization.

flowchart LR
    A["Cost Entries<br/>(Goods, Freight, Customs)"] --> B["Effective FX &<br/>Weight Surcharges"]
    B --> C["Apportion Freight<br/>by Product Weight"]
    C --> D["Landed Unit Cost (BDT)"]
    D --> E["Stamp landed_cost_bdt<br/>on Shipment Items"]
    E --> F["Available for<br/>Stock Allocation & Sales"]

Formula:

Landed Cost (BDT) = (Purchase Price × FX Rate) + Apportioned Cargo Charge + Customs Surcharge

Dual-phase design: in-memory preview in the UI; authoritative stamp written to the database only on shipment finalization.

Tech Stack

Impact & Results

Security & Reliability

• PostgreSQL RLS on all tenant-scoped tables with membership-based policy evaluation
• Atomic RPCs for invoice creation, dropship settlement, shipment finalization, wallet transfers
• Four scoped login surfaces with Google OAuth via Supabase Auth and automatic token refresh
• Type-safe contracts between generated Supabase types and frontend stores/composables
• Archive-first governance for shipments — financial audit trails preserved, no accidental hard deletes
• Soft-delete trash with 30-day retention and tenant-scoped purge engine
• Local-first development — Docker Supabase with full migration replay before any production deploy

What I Built (Personal Contributions)

As Lead Framework & Migration Engineer:

• Designed the parent–child tenant hierarchy and stock allocation model
• Architected the Universal Wallet parent-books consolidation (in progress migration)
• Built the module permission guard system (tenant_modules + module_actions + scope routing)
• Led the schema modularization — splitting monolithic SQL into domain-scoped folders
• Established the page → store → service → repository module pattern across 20+ domains
• Implemented TanStack Query caching strategy with optimistic mutations and batch RPC patterns
• Drove 980+ migrations with local-first Supabase workflow and generated TypeScript types
• Built specialized verticals: Thrift (second-hand retail), Koba (UK cross-border), Dropship Finance Hub

Visual Workflows & Architecture Wireframes

1. Enterprise Desktop Layout — 3-Tier Navigation & Workspace Grid

+----------------------------------------------------------------------------------------------------+
|  [Logo] TradeflowBD  |  [Scope: Parent Corp v]  |  [Global Search Ctrl+K]  |  [FX: ৳170]  | (Avatar) |
+----------------------+-----------------------------------------------------------------------------+
| NAVIGATION           | BREADCRUMB: Wholesale > Procurement > Inbound Shipments > Batch #SH-2026-08 |
|                      +-----------------------------------------------------------------------------+
| [=] Dashboard        | +-- BATCH KPI HEADER -----------------------------------------------------+ |
| [T] Tenants & Desks  | | Port of Origin: Felixstowe, UK   | Containers: 4x 40ft HQ   | Status: IN_TRANSIT| |
| [!] Access Control   | | Total CBM: 142.5 m³             | Net Weight: 18,420 kg    | Landed: ৳8.45M    | |
| [?] Help Center      | +-------------------------------------------------------------------------+ |
| [@] Customers        |                                                                             |
| [#] Invoices (POS)   | +-- ACTION TOOLBAR -------------------------------------------------------+ |
| [>] Procurement      | | [+ Add Items] [Apportion Landed Costs] [Print Thermal Tags] [v Export]   | |
| [*] Product Costing  | +-------------------------------------------------------------------------+ |
| [$] Shop & Dropship  |                                                                             |
| [&] Wallets & Ledger | +-- REAL-TIME PRODUCT APPORTIONMENT TABLE --------------------------------+ |
|                      | | [x] | SKU Code     | Product Name         | Qty  | Unit(£) | Landed(৳) | Margin% | |
|                      | |-----|--------------|----------------------|------|---------|-----------|---------| |
|                      | | [ ] | TOALP001     | Alpecin Shampoo C1   | 1200 | £4.75   | ৳1,280.00 | 18.5%   | |
|                      | | [ ] | TOAQU133A    | Aquafresh Toothpaste | 3500 | £0.75   | ৳380.00   | 14.2%   | |
|                      | | [ ] | TONXT-JKT    | Next Corduroy Jacket | 450  | £12.00  | ৳2,850.00 | 32.0%   | |
|                      | +-------------------------------------------------------------------------+ |
| [<-] Sign Out        | PAGE 1 OF 18 (240 ITEMS)                      [<<] [<] [1] [2] [3] [>] [>>] |
+----------------------+-----------------------------------------------------------------------------+

2. Multi-Tenant Stock Allocation & Landed Cost Engine Workflow

flowchart TD
    subgraph S1 ["1. International Procurement & Cargo Manifest"]
        INVOICE["Supplier Purchase Order<br/>(GBP £ / USD $)"]
        FREIGHT["Sea / Air Freight Costs<br/>(Per kg / Per CBM)"]
        CUSTOMS["Customs Duty, AIT & Port Handling<br/>(Regional Clearing Agents)"]
    end

    subgraph S2 ["2. Automated Landed Cost Engine"]
        INVOICE & FREIGHT & CUSTOMS --> ENGINE["Weight & Value Apportionment Engine<br/>Effective FX Rate Multiplier"]
        ENGINE --> STAMP["Final Landed Unit Cost Stamped<br/>(Per Single Item SKU)"]
    end

    subgraph S3 ["3. Parent Warehouse & Pooled Virtual Stock"]
        STAMP --> POOL["Central Parent Stock Pool<br/>Available-to-Promise (ATP) Queue"]
    end

    subgraph S4 ["4. Multi-Tenant Sales Channels"]
        POOL -->|"RLS Scoped Views"| DESK1["Wholesale POS Desk<br/>(Bulk Invoicing)"]
        POOL -->|"Virtual Reservation"| DESK2["Online Storefront<br/>(B2C B2B Commerce)"]
        POOL -->|"Atomic Holds"| DESK3["Dropship Reseller Network<br/>(3-Tier Commission Desk)"]
    end

    subgraph S5 ["5. Settlement & Treasury Ledger"]
        DESK1 & DESK2 & DESK3 --> RPC_SETTLE["PostgreSQL Atomic RPCs<br/>(place_order, deduct_stock)"]
        RPC_SETTLE --> WALLET["Universal Double-Entry Wallet<br/>(Parent-Books Consolidated Ledger)"]
    end

Future Roadmap

timeline
    title TradeflowBD Roadmap
    section In Progress
        Wallet Parent-Books Migration : Consolidate all ledger writers onto parent books model
        Schema Domain Split : wallet, thrift, investor, permissions modules
    section Planned
        Customs Documentation Generator : Regional compliance rules automation
        Maritime Tracking APIs : Real-time container telemetry integration
        Investor Portal v2 : Withdrawal request workflow beyond read-only reporting
        Capacitor iOS : Mobile inventory companion for iOS