File Uploads vs APIs: Performance Analysis

Processing Excel files traditionally requires uploading, parsing, and calculating for every request. APIs eliminate these steps, resulting in major performance improvements.

Test Setup

We tested a typical pricing calculator:

• 500 formulas across 3 worksheets
• VLOOKUP and INDEX/MATCH functions
• File size: 245 KB
• Test: 1,000 identical calculations

Response Time Comparison

| Metric | File Upload | API | Improvement |

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

| First Request | 2.5-3.5 sec | 150-200ms | 15-20x faster |

| Subsequent (cold) | 2-3 sec | 100-150ms | 15-25x faster |

| Subsequent (cached) | 2-3 sec | 10-20ms | 100-200x faster |

Where Time Goes

File Upload Method

Total: ~2.5 seconds
├── Upload: 400ms (16%)
├── Parsing: 1200ms (48%)
├── Calculation: 800ms (32%)
└── Other: 100ms (4%)

API Method

Total: ~150ms
├── Network: 25ms (17%)
├── Validation: 5ms (3%)
├── Calculation: 90ms (60%)
└── Response: 30ms (20%)

Why APIs Are Faster

1. No File Transfer

// File upload: 245KB every request
const formData = new FormData();
formData.append('file', excelFile);

// API: Just parameters (~100 bytes)
const params = { users: 150, plan: 'enterprise' };

2. No Parsing Required

File uploads must parse Excel format every time. APIs keep Excel loaded and ready.

3. Efficient Caching

APIs can cache at multiple levels:

• Memory cache: <5ms
• Redis cache: <20ms
• Fresh calculation: 100-200ms

File uploads can't cache effectively since files might change.

Real-World Scenarios

Batch Processing

// Processing 100 quotes
// File upload: 100 × 2.5s = 250 seconds
// API: 100 × 0.15s = 15 seconds (parallel)

User Experience

// Interactive calculator
// File upload: 2-3 second wait per calculation
// API: Near-instant response (<50ms cached)

Memory Usage

File Upload

Per request: ~15MB
├── File buffer: 250KB
├── Parsed workbook: 3MB
├── Formula engine: 10MB
└── Temporary objects: 2MB

API

Per request: ~150KB
├── Request data: 1KB
├── Context: 100KB
└── Response: 50KB

Implementation Comparison

File Upload Approach

// Complex parsing and processing
app.post('/calculate', upload.single('file'), async (req, res) => {
  const workbook = XLSX.read(req.file.buffer);
  // Parse sheets, formulas, dependencies...
  // Calculate results
  // Handle errors
  res.json(result);
});

API Approach

// Simple parameter passing
app.post('/calculate', async (req, res) => {
  const result = await excelAPI.execute('pricing', req.body);
  res.json(result);
});

Scaling Considerations

Concurrent Requests

File uploads are limited by:

• Server memory
• Upload bandwidth
• Parsing overhead

APIs scale better:

• Minimal memory per request
• Efficient connection pooling
• Shared Excel instances

Cost Analysis

Estimated server requirements for 100K requests/day:

| Method | Server Size | Monthly Cost |

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

| File Upload | 2-4 large instances | $400-800 |

| API | 1 medium instance | $50-100 |

Best Practices

1. Use Caching

const cache = new Map();

async function calculate(params) {
  const key = JSON.stringify(params);
  if (cache.has(key)) {
    return cache.get(key);
  }
  
  const result = await api.execute('model', params);
  cache.set(key, result);
  return result;
}

2. Batch Requests

// Send multiple calculations at once
const results = await api.executeBatch([
  { inputs: { amount: 1000 } },
  { inputs: { amount: 2000 } },
  { inputs: { amount: 3000 } }
]);

3. Handle Errors Gracefully

try {
  const result = await api.execute('model', params);
  return result;
} catch (error) {
  // Fallback or retry logic
  console.error('Calculation failed:', error);
  return getCachedOrDefault(params);
}

Key Takeaways

1. APIs are 15-200x faster depending on caching
2. Memory usage reduced by 90%+
3. Simpler implementation with fewer lines of code
4. Better scalability for high-volume applications

When to Use Each

Use File Uploads When:

• One-time processing
• Files change completely each time
• No repeated calculations

Use APIs When:

• Repeated calculations
• Consistent business logic
• Performance matters
• Multiple applications need access

Getting Started

1. Upload your Excel to SpreadAPI
2. Define input/output cells
3. Replace file upload code with API calls
4. Monitor performance improvements

Try SpreadAPI - See the performance difference yourself.

Questions? Contact hello@airrange.io