The challenge
A FinTech startup was on a legacy payment processor that charged 2.9% + 30c per transaction plus a $4,500/month platform fee. Throughput was capped at 80 transactions/second. PCI compliance was a constant audit headache. The startup was leaving 35% of revenue on the table to payment processing costs.
Our approach
- 1
Audited the existing payment flow: API calls, failure modes, retry logic, webhook reliability, reconciliation process.
- 2
Designed a parallel-run strategy: new Stripe Connect implementation behind a feature flag, transaction-by-transaction comparison, gradual cutover over 3 weeks.
- 3
Built a custom reconciliation dashboard that compares both processors in real time and alerts on discrepancies.
- 4
Cut over with zero customer-facing downtime. The legacy processor was decommissioned in week 4.
The solution
The new platform uses Stripe Connect with custom account types, automated KYC, instant payouts for eligible merchants, and full PCI DSS compliance inherited from Stripe. Reconciliation runs hourly, with a custom dashboard for the finance team. The platform supports split payments, subscriptions, multi-currency, and 3DS2 natively. Webhook reliability is handled by a custom retry queue with exponential backoff and dead-letter handling.
The outcome
4x
Throughput
320 transactions/second.
-67%
Cost reduction
From 2.9% + 30c to Stripe's tiered pricing.
0s
Downtime
Customer-facing during migration.
100%
Reconciliation accuracy
Across 1.2M transactions.
100%
3DS2 compliance
EU SCA-ready.
$280K
Annual savings
On $40M annual processing volume.
What the client said
“Migrated our legacy Rails app to a modern Next.js + tRPC + Prisma stack in 14 weeks. Zero downtime, zero data loss, and the new admin panel is faster than what our internal team could have shipped in 6 months. The Stripe migration alone was worth it.”
Stack & technologies
- Next.js 16
- React 19
- TypeScript
- Node.js
- PostgreSQL
- Stripe Connect
- tRPC
- Prisma