On-Premises Excel API: Keep Your Data, Scale Your Calculations

SpreadAPI Team••7 min read

On-Premises Excel API: Full Control Over Your Data

Your finance team built a complex pricing model in Excel. Your actuaries maintain risk calculations that took years to perfect. Your tax department has compliance formulas that handle edge cases nobody else understands.

Now you need to scale these calculations across your organization. But there's a problem: your data can't leave your network.

Whether it's GDPR, HIPAA, financial regulations, or internal security policies—cloud solutions simply aren't an option for many organizations. You need the power of API-driven Excel calculations without sacrificing data sovereignty.

The Challenge: Excel at Scale Without the Cloud

Every enterprise faces the same dilemma:

Option A: Rewrite Everything

Rebuild years of Excel logic in Python, Java, or JavaScript. Spend months validating that your new code matches Excel's behavior exactly. Hope you didn't miss any edge cases.

Option B: Manual Processes

Keep emailing spreadsheets around. Accept the errors, version conflicts, and audit nightmares that come with it.

Option C: Cloud API

Use a cloud service, but accept that your sensitive data will be processed on someone else's servers.

None of these options work when you're dealing with sensitive financial models, proprietary pricing logic, or regulated data.

There's a better way.

The Solution: Build Locally, Deploy Internally

SpreadAPI's on-premises solution gives you the best of both worlds: modern API architecture with complete data sovereignty.

Here's how it works:

SpreadAPI On-Premises 3-Step Workflow: Build in Browser, Export Package, Deploy Internally
SpreadAPI On-Premises 3-Step Workflow: Build in Browser, Export Package, Deploy Internally

Step 1: Build in Browser

Everything happens in your browser's memory. Import your Excel file, define which cells are inputs and outputs, test your calculations—all without any data touching external servers.

Your workbook, your formulas, your test data: it never leaves your machine.

Step 2: Export Runtime Package

When you're satisfied with your API definition, click "Export for Runtime." You'll download a small JSON file (typically around 184 KB) that contains:

  • Your complete workbook structure
  • All formulas and cell references
  • Input/output definitions
  • API configuration

This file is everything the runtime needs to execute your calculations.

Step 3: Deploy on Your Infrastructure

Upload the package to SpreadAPI Runtime running on your own servers. Within seconds, you have a fully functional REST API that executes your Excel calculations—entirely within your network.

Enterprise Mode: Zero Cloud by Design

For organizations with strict data policies, SpreadAPI offers Enterprise Mode. When enabled, the "Save to Cloud" option is completely removed from the interface.

This isn't just a hidden button—it's an architectural guarantee. In Enterprise Mode, there's simply no code path that could send your data to external servers. Even accidental data leakage is impossible.

SpreadAPI Data Flow Diagram: All data stays within your private network, no connection to external cloud
SpreadAPI Data Flow Diagram: All data stays within your private network, no connection to external cloud

The Runtime Server: Simple, Secure, Scalable

SpreadAPI Runtime is a lightweight Docker container that runs your Excel calculations. Here's what makes it ideal for enterprise deployment:

No Database Required

The runtime stores everything in simple JSON files on the local filesystem. No PostgreSQL, no MongoDB, no Redis to configure or maintain.

No Outbound Connections

The runtime doesn't phone home, check for updates, or send telemetry. It works perfectly in air-gapped environments with no internet access at all.

Deployment in Minutes

# Pull the image
docker pull spreadapi/runtime:latest

# Run with your service directory
docker run -d \
  -p 3001:3001 \
  -v ./services:/app/services \
  -v ./logs:/app/logs \
  spreadapi/runtime:latest

That's it. Your Excel API is now running on port 3001.

Horizontal Scaling

Need more capacity? Run multiple containers behind a load balancer. Each instance is stateless—they all read from the same service files and can handle requests independently.

# kubernetes deployment example
apiVersion: apps/v1
kind: Deployment
metadata:
  name: spreadapi-runtime
spec:
  replicas: 3
  template:
    spec:
      containers:
      - name: runtime
        image: spreadapi/runtime:latest
        ports:
        - containerPort: 3001
        volumeMounts:
        - name: services
          mountPath: /app/services

Technical Specifications

Supported Excel Features

The runtime supports 500+ Excel functions, including modern array functions:

  • Lookup: VLOOKUP, HLOOKUP, XLOOKUP, INDEX, MATCH
  • Array: FILTER, SORT, SORTBY, UNIQUE, SEQUENCE
  • Modern: LET, LAMBDA, dynamic arrays
  • Financial: NPV, IRR, PMT, all standard financial functions
  • Statistical: Full statistical function library
  • Math & Trig: Complete mathematical operations

Performance

| Metric | Typical Value |

|--------|---------------|

| Cold start (first calculation) | 200-500ms |

| Warm calculation | 10-50ms |

| Complex workbook (1000+ formulas) | 50-200ms |

| Memory per service | 10-50MB |

API Endpoints

GET  /api/health              # Health check and version
GET  /api/services            # List all deployed services
GET  /api/services/{id}       # Get service schema
POST /api/execute/{id}        # Execute calculation
POST /api/upload              # Deploy new service

Execute a calculation:

curl -X POST http://localhost:3001/api/execute/pricing-model \
  -H "Content-Type: application/json" \
  -d '{"inputs": {"quantity": 100, "region": "EU"}}'

Response:

{
  "serviceId": "pricing-model",
  "inputs": { "quantity": 100, "region": "EU" },
  "outputs": {
    "basePrice": 4500,
    "discount": 450,
    "finalPrice": 4050,
    "deliveryDays": 5
  },
  "metadata": {
    "executionTime": "32ms"
  }
}

Compliance Checklist

For organizations evaluating on-premises solutions, here's how SpreadAPI Runtime addresses common compliance requirements:

| Requirement | SpreadAPI Runtime |

|-------------|------------------|

| Data Residency | All data on your infrastructure |

| Data in Transit | Internal network only |

| Data at Rest | Your encryption, your policies |

| Access Control | Integrates with your IAM |

| Audit Logging | Configurable request logging |

| External Dependencies | None—runs fully offline |

| Vendor Access | Zero vendor access to your data |

| Network Isolation | No outbound connections required |

Real-World Use Cases

Financial Services

A European bank runs loan amortization calculations for thousands of customers daily. Their Excel models contain proprietary risk adjustments that can't leave their infrastructure. With SpreadAPI Runtime, they process 50,000+ calculations per day—all within their private data center.

Insurance

An insurance company's actuaries maintain premium calculation models in Excel. These models represent decades of statistical refinement. The runtime lets underwriting systems call these calculations via API while keeping the intellectual property completely internal.

Tax & Compliance

A Big Four consulting firm has VAT calculation templates for 40+ jurisdictions. Client data can never touch external systems. SpreadAPI Runtime runs in their secure client-facing environment, letting consultants generate compliant calculations without manual Excel work.

Manufacturing

An automotive supplier calculates bill-of-materials costs with Excel models containing proprietary margin structures. Their ERP system now calls the runtime API to get real-time cost rollups—no cloud exposure of competitive pricing data.

Getting Started

  1. Try Enterprise Mode: Enable private mode in SpreadAPI and build your first service entirely in-browser.
  1. Export a Package: Test the export workflow with a simple calculation.
  1. Run Locally: Start the Docker container on your machine and verify it works.
  1. Deploy Internally: Move to your staging environment and integrate with your systems.
  1. Scale: Add monitoring, authentication, and horizontal scaling as needed.

Learn More

Questions about deploying in your environment? Contact us at hello@airrange.io

on-premisesdata sovereigntycomplianceenterpriseself-hostedair-gappeddocker