How to Build a Payment System: The Complete Hiring Guide

What Success Looks Like

Before diving into hiring, understand what successful payment systems achieve. Your payment infrastructure is the revenue engine of your business—failures here directly impact the bottom line.

Characteristics of High-Performing Payment Systems

1. High Authorization Rates
Great payment systems achieve 95%+ authorization rates. Every 1% improvement in auth rate directly increases revenue. This requires smart retry logic, proper error handling, and understanding of card network rules.

2. Low Fraud Rates
Balance fraud prevention with customer friction. Target <0.1% fraud rate while maintaining <1% false positive rate. Too strict = lost legitimate customers. Too loose = chargebacks and losses.

3. Fast Settlement
Money should move predictably. Clear visibility into when funds will be available, accurate reconciliation, and minimal float time. For marketplaces, efficient payouts to sellers.

4. Compliance Confidence
Pass audits without scrambling. PCI-DSS compliance is maintained continuously, not achieved annually. SOC 2 controls are embedded in processes, not bolted on.

5. Operational Excellence
Issues are detected before customers report them. Monitoring catches payment failures in real-time. On-call engineers can diagnose and resolve issues quickly.

Warning Signs of Struggling Payment Systems

The Build vs. Integrate Decision

This decision shapes your entire hiring strategy. Get it right before you start building your team.

When to Integrate (Most Companies)

Use payment platforms (Stripe, Adyen, Braintree, PayPal) when:

• Processing under $100M annually
• Standard use cases (e-commerce, SaaS, marketplaces)
• Need to launch quickly (weeks, not months)
• Don't have payments domain expertise
• Payment processing isn't your competitive advantage

Integration team requirements:

Total: 2-4 engineers, $400K-800K annually

Benefits of integration:

• Faster time to market (weeks vs. months)
• Built-in fraud detection and compliance
• Platform handles PCI-DSS burden
• Automatic updates for regulations and card rules
• Lower engineering investment

When to Build Custom (Rare)

Build custom payment infrastructure when:

• Processing $100M+ annually AND margins matter
• Unique requirements platforms can't support
• Payment processing IS your product (fintech)
• Need direct acquiring relationships
• Global scale with specific regional needs

Custom build team requirements:

Total: 6-8 engineers, $1.5M-2.5M annually

Hybrid Approach (Common Path)

Most successful companies evolve through stages:

Stage 1: Pure Integration

• Use Stripe/Adyen for everything
• Focus engineering on core product
• Accept platform fees as cost of speed

Stage 2: Optimize Integration

• Build abstraction layer over payment platform
• Add custom fraud rules
• Optimize checkout conversion

Stage 3: Selective Building

• Direct acquiring for high-volume regions
• Custom fraud models
• Multi-processor routing

Stage 4: Full Control (Rare)

• Payment facilitator (PayFac) model
• Direct card network connections
• Full compliance ownership

Roles You'll Need

For Integration-Focused Teams

Senior Backend Engineer (Payments Focus)

This is your first payments hire. They own the integration with payment platforms and ensure reliable transaction processing.

Key responsibilities:

• Integrate with payment platforms (Stripe, Adyen, etc.)
• Build checkout flows and payment orchestration
• Handle webhooks, retries, and error states
• Implement subscription and recurring billing logic

Must-have experience:

• 5+ years backend development
• Payment platform integration experience
• Understanding of asynchronous processing
• Idempotency and data consistency patterns
  

Checkout/Frontend Engineer

Owns the payment user experience—the last step before conversion.

Key responsibilities:

• Build checkout flows with conversion optimization
• Implement payment forms with proper security
• Handle payment method storage (tokenization)
• Mobile payment experiences (Apple Pay, Google Pay)

Must-have experience:

• Strong frontend skills (React, Vue, etc.)
• PCI-compliant form handling
• A/B testing and conversion optimization
• Accessibility for payment flows

For Custom Build Teams

Payments Technical Lead

The architect who understands both technology and financial domain.

Key responsibilities:

• Payment system architecture and roadmap
• PCI-DSS compliance ownership
• Vendor relationships (processors, acquirers)
• Technical due diligence on payments decisions

Must-have experience:

• 8+ years with 3+ in payments specifically
• Built payment systems at scale
• Deep compliance knowledge (PCI-DSS, SOC 2)
• Experience with multiple payment processors

Security Engineer (Payments)

Payments require specialized security beyond general AppSec.

Key responsibilities:

• PCI-DSS compliance and audit preparation
• Encryption key management
• Fraud detection integration
• Secure payment data handling

Must-have experience:

• PCI-DSS implementation experience
• Hardware security modules (HSMs)
• Tokenization and encryption patterns
• Fraud prevention systems

Data Engineer (Payments)

Financial data requires exceptional accuracy and auditability.

Key responsibilities:

• Payment reconciliation pipelines
• Financial reporting and analytics
• Audit trails and compliance reporting
• Settlement and payout calculations

Must-have experience:

• Financial data modeling
• Reconciliation systems
• High-accuracy data pipelines
• Regulatory reporting

Compliance Considerations

PCI-DSS: The Non-Negotiable

Payment Card Industry Data Security Standard (PCI-DSS) compliance is mandatory if you handle card data. The level of compliance depends on transaction volume and how you handle data.

Compliance levels:

Hiring implications:

Using payment platforms (Stripe, etc.):

• Platform handles most PCI burden
• You're responsible for SAQ-A or SAQ-A-EP
• Need engineer who understands secure integration
• Security review of your integration points

Building custom:

• Need dedicated security engineer (or team)
• Annual QSA audits ($50K-200K)
• Ongoing compliance maintenance
• Security training for all engineers touching payments

Beyond PCI-DSS

Other compliance requirements to consider:

Team Structure

Small Team (Integration Focus)

Engineering Lead
├── Senior Backend Engineer (Payments)
│   └── Owns: Integration, webhooks, billing
├── Frontend Engineer
│   └── Owns: Checkout, payment UX
└── DevOps/Security (shared)
    └── Owns: PCI compliance, infrastructure

Total: 3-4 engineers
Budget: $500K-900K annually

Medium Team (Growing Payments)

Payments Engineering Manager
├── Senior Backend Engineer × 2
│   └── Owns: Core processing, integrations
├── Frontend Engineer
│   └── Owns: Checkout experience
├── Security Engineer (0.5-1 FTE)
│   └── Owns: PCI, fraud rules
└── Data Engineer (0.5 FTE)
    └── Owns: Reconciliation, reporting

Total: 5-6 engineers
Budget: $1M-1.5M annually

Large Team (Custom Build)

VP/Director of Payments
├── Payments Engineering Manager
│   ├── Tech Lead (Architecture)
│   ├── Senior Backend × 3
│   │   └── Owns: Core processing, routing, settlement
│   └── Mid-Level Backend × 2
│       └── Owns: Integrations, operational tools
├── Security Team
│   ├── Security Engineer (Payments)
│   │   └── Owns: PCI, HSM, encryption
│   └── Fraud Engineer
│       └── Owns: Detection, rules, ML models
├── Data Team
│   ├── Data Engineer
│   │   └── Owns: Reconciliation, pipelines
│   └── Analytics Engineer
│       └── Owns: Reporting, metrics
└── Frontend Engineer
    └── Owns: Checkout, payment UX

Total: 10-12 engineers
Budget: $2.5M-4M annually

Common Pitfalls

1. Building Before You Should

The trap: "We'll save money by building our own payment system."

Reality: Payment platforms charge 2.9% + $0.30, but building custom costs $1.5M+ in year one alone. At $10M GMV, platform fees = $290K. You're not saving money until $50M+ volume, and that ignores ongoing maintenance.

Better approach: Integrate first. Build abstraction layer. Migrate to custom only when volume justifies it AND you have payments expertise.

2. Underestimating Compliance

The trap: "PCI compliance is just a checklist."

Reality: PCI-DSS is ongoing, not one-time. Failed compliance means losing ability to process cards. Breaches mean fines, lawsuits, and reputation damage.

Better approach: Hire someone with compliance experience. Budget for audits and tooling. Build compliance into engineering culture from day one.

3. Ignoring Edge Cases

The trap: "We'll handle the happy path first, edge cases later."

Reality: Payments edge cases cause real financial losses: duplicate charges, failed refunds, currency conversion errors, partial captures. Each edge case is a potential customer escalation or revenue leak.

Better approach: Hire engineers who've seen payments at scale. Document and test edge cases thoroughly. Build monitoring for financial anomalies.

4. Underinvesting in Fraud

The trap: "We'll add fraud prevention when we need it."

Reality: Fraudsters find you fast. High chargeback rates trigger processor warnings, fee increases, or termination. Reactive fraud prevention means losses have already occurred.

Better approach: Use platform fraud tools from day one. Monitor fraud metrics continuously. Add custom rules as patterns emerge.

5. Poor Error Handling

The trap: "Card declined? Show an error and move on."

Reality: Vague errors frustrate customers. Missing retry logic loses revenue. Poor error logging makes debugging impossible.

Better approach: Specific, actionable error messages. Smart retry with exponential backoff. Comprehensive logging for every transaction state.

Budget Reality Check

Integration Approach (Most Companies)

*Platform fees scale with volume: $10M GMV = ~$290K fees

Custom Build Approach

When Custom Makes Financial Sense

Break-even analysis (simplified):

• Platform fees at $100M GMV: ~$2.9M
• Custom build cost: ~$2.5M ongoing
• Break-even: roughly $85M-100M+ GMV

But financial break-even ignores:

• Engineering opportunity cost
• Compliance risk
• Time to build (12-18 months)
• Ongoing maintenance burden

Recommendation: Don't build custom until volume exceeds $100M AND you have strategic reasons beyond cost savings.

Recruiter's Cheat Sheet

Key Questions to Ask Candidates

Red Flags in Payments Candidates

• No understanding of idempotency ("charge only once")
• Treats compliance as someone else's problem
• No experience with async processing/webhooks
• Can't explain payment flow from user click to settlement
• Dismissive of edge cases or error handling

Green Flags in Payments Candidates

• Has seen payment systems fail and knows what breaks
• Understands compliance is engineering responsibility
• Thinks about financial accuracy obsessively
• Experience with multiple payment platforms
• Can explain card networks, processors, and acquirers