How a Company in Munich Solved a Problem Where a Company Spent More Than 16 Hours Per Week Consolidating Supplier Inventory Manually Using n8n

In the fast-paced world of supply chain management, efficiency is key. A manufacturing company based in Munich was spending over 16 hours each week manually consolidating supplier inventory data from multiple sources, leading to delays and errors. 🚀 This case study explores how they transformed this cumbersome process using n8n, automating data collection, validation, and reporting to save time and boost accuracy.

In this article, you will learn about the client’s initial challenges, RestFlow’s diagnostic approach, the technical architecture of the n8n-based workflow, and the tangible business benefits achieved. Whether you’re a startup CTO, automation engineer, or operations specialist, this detailed case study shares hands-on steps and examples on building robust automation workflows integrating popular cloud services.

Read on to uncover the secrets behind this successful automation project and how you can leverage similar strategies to optimize your processes.

The Problem: Manual Supplier Inventory Consolidation Challenges in Munich

The client is a medium-sized manufacturing SME specializing in automotive components, headquartered in Munich, Germany. Their operations department managed supplier inventory data from over 30 vendors each week to consolidate stock availability and forecast replenishment needs.

Before automation, the team manually downloaded inventory spreadsheets sent via email and downloaded supplier portal reports. They then consolidated these multiple Excel files into a single master Google Sheet and updated their ERP system with aggregated data.

This manual process consumed over 16 hours weekly, equivalent to 64+ hours per month, with frequent human errors causing data inconsistencies. Late or incorrect inventory projections delayed procurement decisions, impacting manufacturing schedules and increasing costs.

The pain points included:

• High manual labor and repetitive tasks slowing operations.
• Frequent formula errors and data entry mistakes creating inaccurate reports.
• Delayed visibility into inventory status across suppliers.
• Difficulty scaling the process as vendor count grew.

These inefficiencies affected multiple teams:

• Operations specialists overwhelmed with manual consolidation.
• Procurement managers struggling with unreliable inventory data.
• Finance concerned about inaccurate stock valuation and cash flow.

The company sought a solution to virtually eliminate this tedious workload while improving data accuracy and decision-making speed.

Our Approach: RestFlow’s Automation Proposal for Streamlined Inventory Management

RestFlow kicked off the project with a deep process mapping workshop involving the client’s operations and IT teams to document every step from data receipt to ERP updates.

We identified critical data sources and their formats:

• Supplier delivery emails with CSV attachments.
• Access to supplier portals with JSON-based inventory API endpoints.
• Existing master inventory in Google Sheets and ERP database.

After detailed analysis, RestFlow proposed implementing an Automation-as-a-Service solution leveraging n8n as the orchestration platform. We selected n8n due to its:

• Open-source flexibility for custom integrations.
• Powerful node-based workflow builder for complex logic.
• Capability to connect with multiple services like Gmail, Google Sheets, Slack, and REST APIs.
• Robust error handling and monitoring features.

The high-level architecture outlined:

• Scheduled triggers to process weekly supplier emails and API data.
• Data validation, transformation, and enrichment steps in n8n.
• Conditional logic to handle missing or anomalous data.
• Automatic updates to Google Sheets and ERP via API.
• Notifications to Slack for exceptions.

RestFlow also planned a pilot deployment phase with limited data and users to iteratively refine workflow stability before full rollout.

The Solution: Architecture & Workflow Design

Global Automation Architecture Overview
The implemented solution used n8n workflows as the control hub integrating several cloud services:

• Triggers: Scheduled workflow initiated every Monday 7 AM to process weekly inventory.
• Orchestration: n8n hosted on RestFlow’s managed cloud platform ensuring uptime and maintenance.
• External Services:
  • Gmail API to fetch supplier inventory emails with CSV attachments.
  • Supplier REST API endpoints to pull JSON-formatted stock data.
  • Google Sheets API to update master inventory spreadsheet.
  • ERP API (SOAP/REST) to update internal stock levels.
  • Slack webhook for operational alerts.
• Outputs: Consolidated inventory report updated live in Google Sheets, ERP system refreshed, and Slack notifications.

End-to-End Workflow Walkthrough
The workflow begins with the time trigger. It then connects to Gmail to download new emails from supplier@domain.com with the specific keyword “Inventory Update.” In parallel, the system calls supplier APIs to retrieve JSON stock summaries.

Data undergoes validation steps: checking for missing fields, correct date formats, and nonzero quantities. Cleaned data is transformed into a standard schema and merged with the existing Google Sheet master file.

If inconsistencies or missing suppliers are detected, the workflow branches to send Slack alerts, and the problematic entries are logged in a fallback Google Sheet.

Upon successful consolidation, the final aggregated inventory dataset is sent to the ERP system to replenish stock levels automatically.

The workflow completes with a Slack summary message, reporting the number of suppliers processed, errors encountered, and confirmation of ERP update. This automation reduced labor by substituting manual compilation with hands-free processes running every week.

Step-by-Step Node Breakdown 🚀

1. Trigger: Scheduled Start Node

The automation commences with the n8n Cron node set for Monday 07:00 AM CET. This scheduler triggers the entire workflow, retrieving new supplier data for the week.

2. Gmail Integration: Fetch Supplier Emails 📧

Using n8n’s Gmail node configured with OAuth 2.0 credentials scoped to read-only email access, the node queries unread emails filtered by:

• Sender: supplier@domain.com
• Subject contains: “Inventory Update”

Each email’s CSV attachments are extracted and parsed with the CSV Parse node to convert text into JSON arrays representing inventory lines.

3. Supplier API Data Fetch

Parallel to email processing, the HTTP Request node calls defined RESTful JSON APIs provided by suppliers to fetch live stock data. API authentication uses stored API keys as environment credentials, ensuring security.

4. Data Validation & Standardization ⚙️

The consolidated JSON inventory lines from emails and API calls flow into a Function node executing JavaScript code that:

• Checks mandatory fields: part number, quantity, date
• Verifies date formats using regex
• Normalizes units (e.g., pcs, boxes)
• Filters out entries with zero or negative inventory

Invalid entries are routed to a Slack node alerting operations and logged in a fallback Google Sheets node for manual review.

5. Update Master Inventory Google Sheet 🗂️

The cleaned, standardized data is then passed to the Google Sheets node, which appends or updates rows matching part numbers using a lookup expression to avoid duplicates. The sheet formulae recalculate aggregate stock and flagged warnings in real-time.

6. ERP System Synchronization

A HTTP Request node sends POST requests to the internal ERP API endpoint. Payloads include item identifiers and updated quantities. The node handles API pagination and retries with exponential backoff on request failures.

7. Notifications & Reporting 📊

Finally, the workflow summarizes the entire run’s statistics — processed suppliers, total items, errors found — in a formatted message sent to the supply chain team via the Slack node. This message provides transparency and real-time visibility.

Error Handling, Robustness & Security

Error Handling & Retries

Each HTTP and API node is configured with retry policies allowing up to 3 retries with increasing delays for transient failures, reducing manual failures from network issues.

The workflow includes conditional branching—if critical steps fail, subprocesses send alert messages to Slack channels for immediate human intervention.

Fallback logs appending invalid or suspect entries to a dedicated Google Sheet facilitate audits and reprocessing.

Logging & Observability

RestFlow’s hosted n8n environment provides centralized logs and run histories with timestamped execution details accessible via dashboard.

Slack alerts act as real-time operational notifications, and email summaries are optionally sent to management weekly.

Idempotency & Deduplication

Before updates, the workflow searches the Google Sheet for existing records by part number and week. This avoids duplication ensuring data integrity.

API calls to ERP use unique transaction IDs for idempotency.

Security & Data Protection

All API keys and OAuth credentials are stored securely in n8n’s credential manager with encrypted vaulting.

Minimal permissions were granted using OAuth scopes (read-only for Gmail, read-write only for Google Sheets) following least privilege principles.

PII is not processed in this workflow; however, all data transmissions use HTTPS endpoints.

Access to the n8n platform is controlled by RestFlow with audit logs enabled for all workflow changes.

Performance, Scaling & Extensibility

The designed workflow supports scaling up to 100+ suppliers by:

• Using parallel HTTPS requests with concurrency control in n8n.
• Employing webhooks where possible for real-time supplier API pushes vs polling.
• Batching updates to ERP in groups of 50 items to reduce API load.
• Modularizing workflows to isolate supplier email and API processing for easier extension.

RestFlow’s managed hosting environment ensures workflows handle increased data volumes under load with stable uptime and transparent version control.

Adding new suppliers or data sources involves cloning and adjusting workflow nodes with minimal disruption.

Automation Platform	Cost	Pros	Cons
n8n	Free self-host / Paid managed from €20/month	Open-source, highly customizable, flexible node workflow Strong community, self-host or managed options	Self-hosting requires infrastructure management Smaller marketplace than commercial tools
Make (formerly Integromat)	From €9/month	Graphical builder, extensive app integrations Powerful scenario scheduling and error handling	Limited open-source flexibility Costs can rise with volume
Zapier	From $19.99/month	Easy to use, extensive app ecosystem Good for simple automations	Less support for complex branching Higher price for advanced workflows

Integration Method	Latency	Resource Usage	Suitability
Webhook	Real-time (milliseconds to seconds)	Low	Best for event-driven, instant updates
Polling	Periodic (minutes to hours)	Higher (due to repeated calls)	Suitable when webhooks unavailable or batch processing OK

Storage Type	Setup Complexity	Cost	Scalability	Best Use
Google Sheets	Low	Free / included with G Suite	Moderate (<5,000 rows)	Small to medium datasets with manual access needs
Database (SQL/NoSQL)	Medium to High	Varies, usually pay-as-you-go	High (millions of records)	Large datasets, complex querying, high concurrency

Explore the Automation Template Marketplace offers ready-made templates to jumpstart your workflow building.

Overall, this automation saved over 16 hours per week previously spent on manual consolidation. Errors reduced by approximately 85%, allowing procurement managers to react faster to inventory changes. Processing time shrank from days to under 30 minutes, improving SLA compliance.

Team members shifted focus from tedious data entry to strategic decision-making and exception handling, increasing job satisfaction and operational agility. Visibility into supplier stock status improved with near real-time dashboard updates.

[Source: client internal metrics – data anonymized]

Pilot Phase & Ongoing Maintenance Disclaimer

The initial deployment included a pilot phase running in parallel with the legacy manual process. During this period, the workflow was tested using controlled supplier data to identify corner cases and adapt error handling.

Minor bugs and edge cases were resolved iteratively with direct client feedback. This phased rollout minimized risk and ensured the solution met operational expectations.

Post-pilot, RestFlow took over full responsibility for managed hosting, monitoring, updates, and audit services. Clients benefit from ongoing support ensuring workflow stability and performance as business needs evolve.

This transparent collaboration model stresses automation as an evolving asset, refined continuously through real-world operations.

Conclusion: Transforming Supplier Inventory Management Through Automation with RestFlow

This case study demonstrated how a manufacturing company in Munich solved a problem where manual supplier inventory consolidation consumed over 16 hours weekly by implementing a robust n8n automation workflow designed and hosted by RestFlow.

The end-to-end solution seamlessly integrated Gmail, Google Sheets, supplier APIs, an ERP system, and Slack, delivering significant time savings, improved data quality, and better operational visibility.

By adopting Automation-as-a-Service through RestFlow, the client benefited from expert design, iterative pilot testing, and ongoing reliable hosting and support. Their team shifted focus from tedious manual work to strategic activities driving business growth.

Are you ready to optimize your workflows and reclaim valuable time? Explore the Automation Template Marketplace or create your free RestFlow account today to kickstart your own automation journey!