Build vs Buy: Custom Fields for Your SaaS Product

Your customers are asking for custom fields. Your engineering team estimates 3-6 months. Product keeps deprioritizing it because there's always something more urgent.

This is the build-vs-buy decision. Here's the data.

The Real Cost of Building

Engineering Time

The total cost of building is typically 3-4x the original estimate once you account for development, maintenance, security, and training.

Source: Appinventiv - Build vs Buy

Ongoing Maintenance

After the initial build, maintenance costs 15-20% of the build cost annually. That includes:

• Bug fixes and edge cases
• New field type requests
• Performance optimization as data grows
• Security patches
• Database migration management
• UI updates to match product redesigns

"Ongoing maintenance, security updates, and scaling efforts add to the total cost of ownership" - Joyfill

Opportunity Cost

Every sprint your team spends on custom fields infrastructure is a sprint not spent on:

• Features that differentiate your product
• Performance improvements
• New integrations customers are requesting
• Revenue-generating work

The Cost of Buying

Integration time: hours, not months. Maintenance: zero (the service handles it).

The Decision Framework

Build if ALL of these are true:

• Custom fields are your core product differentiator
• You have a dedicated platform engineering team (5+ engineers)
• You have unique requirements no service can meet
• You're willing to commit to ongoing maintenance

Buy if ANY of these are true:

• Custom fields are a feature, not your product
• Your team has fewer than 100 engineers
• You need to ship in days or weeks, not months
• You'd rather spend engineering time on core product

71% of tech teams choose off-the-shelf solutions to accelerate time-to-value. For teams under ~100 engineers, the math rarely favors building infrastructure.

Source: Chameleon - Build vs Buy

What "Buying" Actually Looks Like

With Kopra, the integration is:

1. Your backend generates a token (one API call):

curl -X POST https://api.kopra.dev/api/auth/token \
  -H "X-API-Key: kp_your_key" \
  -H "Content-Type: application/json" \
  -d '{"tenantId": "tenant-123", "fieldGroupKey": "customer"}'

2. Your frontend loads the SDK (5 lines):

import { KopraSDK } from '@kopra-dev/sdk';

const sdk = new KopraSDK({
  currentTenant: 'tenant-123',
  getToken: async (req) => {
    const res = await fetch('/api/kopra-token', {
      method: 'POST',
      body: JSON.stringify(req),
    });
    return res.json();
  },
});

await sdk.loadCustomFields('container', {
  fieldGroupKey: 'customer',
  entityId: 'contact-42',
});

3. Your customers configure their own fields. No engineering tickets.

That's it. Your team ships this in an afternoon and moves on to the work that actually differentiates your product.

Try Kopra free - no credit card required.