How to Define Requirements for Payment, Map, SMS, and Email API Integrations
A guide for clients on defining requirements and comparing vendors for commonly used API integrations (payment, map, SMS, email) in outsourced software development.
- •Organizing required accounts, authentication details, and costs per API integration in advance can shorten the development timeline by 1-2 weeks.
- •Payment API integration requires PG (Payment Gateway) selection and a business review that takes 1-7 business days.
- •SMS and email services are billed per message, so calculate your estimated monthly volume in advance.
Payment API Integration
Payment Gateway (PG) Comparison:
| PG Provider | Fees | Integration Difficulty | Documentation Quality | Features |
|---|---|---|---|---|
| Toss Payments | 2.5-3.5% | Low | Excellent | Modern API, startup-friendly |
| PortOne (formerly iamport) | PG fees only | Low | Excellent | Multi-PG integration, free |
| KG Inicis | 2.5-3.5% | Moderate | Moderate | #1 market share, legacy |
| NHN KCP | 2.5-3.5% | Moderate | Moderate | Stable, suited for large-scale |
| Kakao Pay | 2-3% | Low | Excellent | Simple payment, popular with younger users |
What the Client Should Prepare:
Recommendation: For startups and MVPs, PortOne (formerly iamport) is recommended. It is free and integrates multiple PGs (Toss, Kakao, Inicis, etc.) through a single API for maximum flexibility.
Cost Consideration: Transaction fees (2.5-3.5%) are deducted directly from revenue, so calculate estimated fee costs based on your projected monthly revenue.
Map API Integration
Map Service Comparison:
| Service | Free Tier | Overage Cost | Korea Data Quality | Best Suited For |
|---|---|---|---|---|
| Kakao Maps | 300K requests/day | Paid conversion | Best | Domestic services (recommended) |
| Naver Maps | Monthly free tier | Paid conversion | Excellent | Domestic services |
| Google Maps | $200 monthly credit | Per-request billing | Moderate | Global services |
Map API Requirements Checklist:
Recommendation: For domestic services, Kakao Maps offers the best data accuracy and free tier limits. For global services, choose Google Maps but watch the costs carefully.
SMS and Email API Integration
SMS Service Comparison:
| Service | Cost Per Message | Features |
|---|---|---|
| Aligo | 9.9-16.5 KRW | Cheapest, #1 in Korea |
| Naver Cloud SMS | 9-15 KRW | Stable, bulk messaging |
| AWS SNS | ~5-7 KRW | Global, English documentation |
| Kakao Alert Talk | 7-8 KRW | Kakao-based, high delivery rate |
Email Service Comparison:
| Service | Free Tier | Overage Cost | Features |
|---|---|---|---|
| AWS SES | 62,000/month (with EC2) | $0.10 per 1,000 messages | Most affordable |
| SendGrid | 100/month | Paid plans | Marketing email features |
| Mailgun | 100/month | Paid plans | Developer-friendly |
| Stibee | 500/month | Paid plans | Korean language, newsletters |
Messaging Requirements Checklist:
API Integration Cost Summary (Monthly Estimates)
Here is an estimated monthly operating cost breakdown for an MVP.
| API | Monthly Usage (MVP) | Monthly Cost |
|---|---|---|
| Payment (PG) | 100 transactions x avg. 30,000 KRW | ~90,000 KRW in fees |
| Maps (Kakao Maps) | 1,000 requests/day | Free |
| SMS (Aligo) | 1,000 messages/month | ~10,000-16,000 KRW |
| Email (AWS SES) | 5,000/month | Nearly free |
| Kakao Alert Talk | 2,000/month | ~14,000-16,000 KRW |
| **Total** | **~120,000-150,000 KRW + PG fees** |
Key takeaway: API costs scale with usage, so they are not a significant burden in the early MVP stage. However, costs grow as usage increases, so set up monthly cost alerts.
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