A fintech platform's onboarding system had no documentation, and the engineers who understood it had already left.
The Software House rebuilt that onboarding system from the inside and migrated every user to a new KYC provider without forcing a single re-verification.
Partnership goal:
→ To keep onboarding fully intact while migrating every user to the new KYC provider.
About the client
*This information describes a real project, but The Software House cannot disclose the client’s name.
The platform is a regulated digital asset service in the United States that lets users hold, move, and spend digital assets from a single account, backed by institutional-grade compliance and custody.
Onboarding sits at the center of the product, since Know Your Customer verification decides whether a user can access the platform at all.
INDUSTRY
Fintech
REGION
the United States
SERVICE
Legacy system modernization
KYC integration
Onboarding infrastructure
Business context
Two separate problems stood between the platform and a safe onboarding migration.
No documentation existed, and the domain expertise to explain the legacy system had left with the original developers.
The legacy system used a synchronous design that conflicted with the new KYC provider's asynchronous, webhook-driven model.
In practice, the legacy system expected an immediate response, whereas the new KYC provider sent results only later via a separate webhook.
A failed migration risked forcing already-onboarded users to undergo identity verification again, a risk that threatened trust in a platform built entirely on trust.
This mismatch meant no one could touch onboarding without risking an invisible break, so the platform could not decommission its legacy system until every dependency was mapped and stabilized.
Challenges
No documentation existed to explain how onboarding worked.
The original developers left, taking the domain onboarding expertise with them.
The onboarding system used a design incompatible with the new provider's webhooks.
Users faced the risk of repeated identity verification during migration.
The team needed to monetize the platform without new instability.
Decommission legacy system and migrate onboarding without disrupting existing users.
Process
1. Legacy system reverse engineering
A fintech-native team reverse-engineered the onboarding system from the ground up, closing the expertise gap the original developers left behind.
That work made the team the platform's primary subject matter experts for onboarding.
The platform regained the technical expertise and documentation it had lost.
2. KYC vendor migration
With that expertise in place, the legacy KYC vendor gave way to the new KYC provider.
The team coordinated the full switch without interrupting onboarding for existing users.
Onboarding continued without a single user noticing the vendor had changed underneath them.
3. Asynchronous architecture
That switch introduced a new problem, since the legacy system's synchronous calls could not talk directly to the new provider's webhooks.
Middleware built to bridge the two lets onboarding data move between them without a full rewrite.
The platform kept onboarding running without a ground-up rebuild of the system behind it.
4. KYC data portability flow
That same connection also carried verified KYC data, moved securely between platform instances.
Already onboarded users kept their status and skipped identity verification a second time.
Users kept the onboarding status they had already earned, with nothing to redo.
5. Fiat fee module
With onboarding fully protected, the team turned to monetization and built a transaction fee system for platform fund movements.
This module gave the platform a direct way to earn from activity once a user had been onboarded.
The platform gained a new, direct revenue stream tied to onboarded users.
6. P2P gift module
Alongside the fee system, a gift module allows onboarded users to send USD directly to one another.
The feature added a high-demand capability without extra friction for either side.
The platform added a high-demand feature available to every onboarded user.
→ A Swiss fintech automated investor onboarding from signup to trade-ready
Outcomes
A migration that once threatened to break onboarding ended without a single user noticing.
→ Migrated onboarding without forcing a single re-verification.
The KYC data portability pipeline allows already-onboarded users to retain their verified status during the move.
→ Made the entire migration feasible and lower risk.
Every onboarding dependency was mapped and stabilized before a single user was moved to the new KYC provider.
→ Expanded platform revenue and utility.
New fee and gift transfer features gave onboarded users fresh, direct ways to use the platform.
→ Eliminated the platform's single point of failure.
Onboarding documentation no longer depended on any one person, since The Software House established full technical knowledge of the system.
