Multi-Platform API Gateway

Project Overview

A wholesale distribution company operating with three core platforms — QuickBooks for accounting, Salesforce for sales and customer management, and a legacy on-premise ERP for warehouse and inventory — had no automated connection between them. Inventory levels in the ERP were not reflected in Salesforce until a sales rep manually checked. Invoices created in QuickBooks had to be manually reconciled against ERP shipment records. The data discrepancy was causing overselling, delayed billing, and weekly all-hands reconciliation meetings.

We built a custom API gateway that serves as the single integration layer for all three systems — creating one source of truth for inventory, orders, and billing data across the entire operation.

The Challenge

The three platforms had no native integration paths that could handle the client's specific workflows. QuickBooks Online's API provided limited write access. The legacy ERP exposed data only via scheduled flat-file exports. Salesforce required custom object mapping to reflect the company's non-standard order lifecycle. Off-the-shelf iPaaS tools had tried and failed — the ERP file format was too non-standard, and latency requirements made scheduled sync insufficient.

• Sales reps were quoting inventory levels that were already committed or depleted in the ERP
• Billing was 5–12 days behind shipments due to manual cross-referencing between QuickBooks and the ERP
• No single customer view — order history lived in Salesforce, payment status in QuickBooks, fulfillment data in the ERP
• Weekly reconciliation meetings consumed 4–6 hours of management and finance staff time

The Solution

We designed a middleware gateway that sits between all three platforms, translates data models, manages conflict resolution, and maintains a canonical data store that each system reads from and writes to through the gateway.

• ERP File Adapter: A polling service ingests the ERP's flat-file exports every 60 seconds, parses inventory and fulfillment events, and normalizes them into the canonical data model
• QuickBooks Sync: Invoice creation and payment status are synced bidirectionally via the QBO API — new orders trigger draft invoices automatically, and payment confirmations update order status in Salesforce
• Salesforce Integration: Custom opportunity and order objects in Salesforce are kept in sync with real inventory levels — sales reps see live available-to-promise quantities, not stale snapshots
• Conflict Resolution Engine: When conflicting updates arrive from multiple systems within the same sync window, the gateway applies a defined authority hierarchy to resolve correctly
• Unified Customer View API: An internal endpoint aggregates customer order history, payment status, and fulfillment data from all three systems into a single structured response — usable by any internal tool or dashboard

Technical Architecture

Key Results

• Overselling incidents reduced to zero in the 8 months since deployment — Salesforce now reflects real-time ERP inventory
• Weekly data reconciliation meetings cancelled entirely — the gateway resolved the discrepancies that necessitated them
• Finance team manual reconciliation labor reduced by approximately 18 hours/week
• Sales team close rate improved 11% — attributed to accurate inventory data enabling confident quoting
• Gateway has processed over 40,000 sync events since launch with a 99.97% success rate

Interested in a Similar System?

If your business runs on platforms that don't talk to each other — and your team is filling the gaps manually — a custom integration layer can eliminate that overhead entirely. We specialize in connecting systems that weren't designed to connect.

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